How Much of a Calorie Surplus Do You Need to Build Muscle?

A calorie surplus for muscle gain does not automatically need to be large. Most natural lifters do not need 500 calories per day or more above maintenance to build muscle. [3,6–9]

A defensible starting point for many lifters is somewhere between maintenance and approximately 5–10% above estimated maintenance, often translating to roughly 100–300 extra calories per day. That is a practical starting range, not a scientifically established optimum. The appropriate intake depends on your training experience, starting body composition, current bodyweight and goals. [6–9,16]

A calorie surplus can be useful, particularly when you are lean, underweight, under-fuelled or deliberately trying to increase your total bodyweight. But a surplus is not strictly required every time muscle is gained. People can build muscle around maintenance and, under the right circumstances, while losing body fat. [3–5]

The important distinction is:

A calorie surplus is not always necessary for muscle growth.

That does not mean:

A calorie surplus can never improve the probability or rate of muscle growth.

Energy deficits generally reduce lean-mass gains on average. At the same time, the limited direct research comparing maintenance, smaller surpluses and larger surpluses shows that faster weight gain increases body fat more reliably than it increases measured hypertrophy. [3,6–8]

The practical goal is not to maximise how quickly the scale moves. It is to eat enough that inadequate energy intake is unlikely to limit productive training and adaptation, without accumulating substantially more body fat than your goal requires.

What is a calorie surplus?

A calorie surplus means consuming more energy than your body uses over time. For example, if your average maintenance intake is 2,500 calories per day, eating an average of 2,650 calories creates an estimated 150-calorie daily surplus.

For muscle gain, the purpose of a surplus is to reduce the chance that inadequate energy limits productive training and adaptation. It does not guarantee that every extra kilogram will be muscle. Larger surpluses increase body fat more reliably than they increase measured muscle growth. [6–9]

What causes muscle growth?

Resistance training provides the primary external stimulus for hypertrophy by exposing active muscle fibres to mechanical tension. Muscle cells sense that force and convert it into biochemical signals, a process called mechanotransduction. These signals activate pathways involved in producing new muscle proteins, including mTORC1-dependent and independent pathways. Across repeated training sessions, the accumulation of contractile and structural proteins can enlarge the trained muscle fibres. The exact signalling process is complex and not completely understood, but mechanical loading from appropriately programmed resistance training is the central stimulus. [1]

Muscle proteins are continually being synthesised and broken down. Long-term growth requires the cumulative balance between synthesis and breakdown to favour the addition of muscle protein. Dietary protein supplies the amino acids needed for this process, while adequate energy availability helps support training, recovery, protein turnover and tissue synthesis. [1,9,19–21]

However, an acute increase in muscle protein synthesis does not translate directly into a predictable amount of new muscle. Early in a new training programme, some of the increase in myofibrillar protein synthesis reflects repair and remodelling associated with unfamiliar muscle damage rather than the direct addition of new muscle tissue. Damas and colleagues found that the association between integrated myofibrillar protein synthesis and hypertrophy emerged only after this early muscle-damage response had largely subsided. [2]

Food therefore does not independently force unlimited muscle growth.

Training creates the adaptive demand. Protein provides building material. Energy intake helps support the process. Once the training stimulus and nutritional requirements are adequately supported, there is no evidence that doubling the calorie surplus doubles the muscle-building response. [1,6–9]

Do you need a calorie surplus to build muscle?

No. A surplus is not universally required.

Can you build muscle at maintenance?

Yes. Building muscle at maintenance may be more likely, or easier to detect, when you:

• are relatively new to effective resistance training, although being new is not a requirement;

• have resumed training after a break;

• carry enough body fat to support simultaneous fat loss;

• have substantially improved your training quality, effort or protein intake;

• or previously trained inconsistently.

Advanced lifters may also build muscle at maintenance. Their progress is likely to be slower and harder to measure over short periods, and direct long-term comparisons between maintenance and a very small surplus are lacking. [6,8,16]

A 2026 ten-week trial reported that resistance-trained adults assigned to estimated maintenance calories or a prescribed 250-calorie deficit each increased DXA-measured fat-free mass by approximately 1 kg while reducing fat mass. [5]

This supports the possibility of body recomposition outside complete beginners under favourable conditions, but it does not isolate the effect of energy intake.

Actual energy intake and the achieved between-group difference were not quantified. DXA fat-free mass is not a direct measure of new skeletal muscle, and the prescribed groups received dietary support and supervised resistance training while the habitual-diet control did not receive equivalent support. Differences in training supervision and accumulated training volume therefore limit any claim that maintenance and a deficit were equivalent for hypertrophy. The study was also small, and the prescribed groups consumed approximately 2.5 g/kg/day of protein. [5]

The appropriate conclusion is that body recomposition can occur around estimated maintenance or a prescribed small deficit in some resistance-trained people. The trial does not establish that these energy intakes are equivalent for hypertrophy or that maintenance matches a surplus over the long term.

Can you build muscle in a calorie deficit?

Sometimes.

Longland and colleagues placed young men with overweight in a substantial energy deficit for four weeks while they completed an intensive supervised exercise programme. The group consuming 2.4 g of protein per kilogram per day increased lean body mass by approximately 1.2 kg while losing substantial fat. The lower-protein group lost fat but gained virtually no lean mass. [4]

This is clear evidence of body recomposition, but several features of the study made that outcome more likely:

• the participants carried appreciable body fat;

• the intervention was short;

• the higher-protein group consumed 2.4 g/kg/day of protein;

• and the training programme was demanding and supervised.

Across the broader literature, increasing energy deficiency makes lean-mass gain harder. Murphy and Koehler found that resistance training during an energy deficit produced less lean-mass gain on average than resistance training without an energy deficit, while strength gains were less affected. The frequently quoted estimate that a deficit of approximately 500 calories per day would eliminate the average lean-mass gain came from a meta-regression across varied studies. Only seven studies provided direct within-study deficit-versus-control comparisons, while the broader modelling also used deficit studies matched with separate control literature and estimated energy deficits. The figure is therefore a useful population-level warning, not a biological cutoff for an individual. [3]

Body recomposition is most likely when several favourable factors occur together:

• meaningful body-fat stores;

• little previous high-quality resistance training or a return after detraining;

• an effective programme;

• adequate protein;

• and a deficit small enough to preserve productive training. [3–5,17]

The appropriate energy strategy therefore depends on more than training status. A beginner carrying substantial body fat may be well suited to maintenance or a moderate deficit. A lean or underweight beginner with high muscle-gain potential may benefit from a purposeful surplus. An advanced lifter at a reasonable body-fat level may be able to progress at maintenance or with a very small surplus, although the exact advantage of either approach remains uncertain. [3–8]

Energy balance and likely muscle-gain outcomes

This summary reflects direct evidence, indirect evidence and practical inference rather than a proven dose-response curve. [3–8,16]

Does a larger calorie surplus build more muscle?

The direct evidence is much thinner than the confidence of many traditional bulking recommendations suggests.

Small versus large surpluses in trained lifters

Helms and colleagues randomised resistance-trained lifters to estimated maintenance calories, an approximately 5% surplus or an approximately 15% surplus during eight weeks of resistance training. Twenty-one people were randomised and 17 completed the study. [6]

The larger-surplus condition did not produce a general hypertrophy advantage proportionate to its greater energy intake. Faster bodyweight gain was more clearly associated with increased skinfold thickness than with additional muscle growth. There was some indication that faster gain may have favoured biceps growth, and the high-surplus group improved bench-press strength more, but the sample was too small and the study too short to establish a dependable general benefit. [6]

This does not prove that surplus size never affects hypertrophy. Eight weeks is short for detecting small differences in trained lifters, and the realised separation in energy intake and bodyweight gain between groups was imperfect.

It does provide little support for the assumption that moving from a small surplus to a substantially larger one broadly accelerates muscle gain.

Faster versus slower weight gain in athletes

Garthe and colleagues compared a structured higher-intake intervention with usual intake in 39 elite athletes from different sports over approximately 8–12 weeks. The intervention produced substantially greater total bodyweight and fat gain without a statistically significant advantage in total lean-body-mass gain. However, the intervention also changed protein intake and nutrition counselling, dietary intake was not measured identically between groups, and DXA lean body mass is not a direct measure of skeletal-muscle hypertrophy. The study therefore supports the direction that faster gain can increase fat more clearly than lean tissue, but it cannot isolate surplus size as the only cause. [7]

Additional carbohydrate energy in experienced lifters

A 2026 crossover trial in 20 experienced men compared protein-only and protein-plus-carbohydrate supplementation across two eight-week phases. Participants averaged nearly ten years of resistance-training experience. The carbohydrate supplement was designed to add approximately 200 calories per day. Reported total energy intake was about 485 calories per day higher during that phase, but this difference was not consistent with the smaller reported macro and carbohydrate contrasts, so the true achieved energy difference is uncertain. The higher-energy phase did not produce clear benefits for DXA lean mass, ultrasound muscle size, strength or measured fatigue resistance. [8]

This was a crossover study, meaning each participant completed both nutrition conditions one after the other and acted as his own comparison. That can reduce differences between participants, but hypertrophy has no true washout period: muscle gained during the first phase remains when the second phase begins. Order and phase effects can therefore blur the comparison. The researchers statistically adjusted for these issues and also analysed only the first phase as a sensitivity check, but the design still limits certainty. [8]

The study should not be treated as definitive. Its small sample, crossover design and wide confidence intervals do not prove equivalence or rule out a meaningful smaller effect. It nevertheless provides no convincing evidence that adding a modest-to-large amount of carbohydrate energy automatically improves adaptation when protein intake and training are already adequate. [8]

What the combined evidence suggests

The available evidence supports three conclusions:

• A larger surplus will generally make bodyweight rise faster.

• It will probably increase fat gain more reliably.

• It has not been shown to increase hypertrophy in direct proportion to the additional calories.

The evidence is not strong enough to identify the exact surplus that maximises muscle growth.

It is strong enough to question automatically prescribing a large surplus of 500 calories per day or more to every lifter regardless of body size, training status, body composition or goal. [6–9]

That does not mean a larger surplus is never appropriate. A lean or underweight beginner can potentially gain muscle faster than an advanced lifter and may also need to increase total bodyweight substantially. A moderate surplus may therefore be a sensible practical choice. However, no trial has shown that beginners require a larger surplus or that a larger surplus improves their muscle-to-fat gain ratio.

The reverse also matters. Advanced lifters do not automatically need a larger surplus because muscle growth is harder. Their potential rate of new-muscle gain is usually slower, so forcing a clearly visible rate of weekly weight gain may cause the surplus to outpace the tissue they can realistically build. Maintenance or a very small surplus may be appropriate when body-fat levels, training quality and recovery are adequate. Whether a small surplus produces more long-term hypertrophy than maintenance remains uncertain. [6,8,16]

How many calories does it take to build 1 kg of muscle?

An August 2026 bioRxiv preprint estimated that building 1 kg of wet human skeletal muscle requires approximately 3,204–3,710 calories of total food-energy equivalent under its model. The central estimate was 3,481 calories. [38]

This number is easy to misread. It estimates the energy associated with producing the muscle. It does not say that every person must eat a 3,481-calorie surplus to gain the kilogram.

What does the 3,481-calorie estimate include?

The model divides the central estimate into two practically useful parts:

• Approximately 1,355 calories are retained in the new muscle. This is chemical energy stored in the muscle’s protein, intramuscular fat and glycogen. [38]

• Approximately 2,126 calories are expended during the process. This includes the energy involved in synthesising and depositing the tissue, the imperfect efficiency of those processes, maintaining the muscle as it accumulates and processing the additional food. [38]

The 1,355 calories are not an accidental leftover. New muscle contains chemical energy, so supplying the energy retained in the finished tissue is part of constructing it.

Put simply, the model’s central estimate can be understood as:

3,481 calories of total input equivalent = 2,126 calories expended during the process + 1,355 calories retained in the completed muscle.

It does not mean that all 3,481 calories are stored in the body.

What would that look like per day?

The paper used a reference example in which 1 kg of muscle accumulated gradually across 84 days. If additional food supplied the entire modelled cost:

• approximately 41 calories per day would enter as additional food-energy equivalent;

• approximately 25 calories per day would be expended during the process;

• and approximately 16 calories per day would remain stored in the new muscle. [38]

The 41-calorie figure is therefore the modelled total input equivalent. The 16-calorie figure is the average net energy stored if every other body store remains unchanged. Neither figure is a practical daily calorie target. Both are smaller than the normal error involved in tracking food and estimating maintenance intake.

Energy cost is not the same as a required surplus

The model estimates how much energy is associated with building the tissue. It does not establish where every calorie must come from.

The energy can come from additional food, existing body-energy stores or a combination of both. Fat does not turn into muscle, but energy released from body fat can help fund muscle construction. This is one reason gaining muscle while losing fat is physiologically possible in suitable circumstances. [3–5,38]

A lean, underweight or chronically under-fuelled person may need more of the cost supplied by additional food. Someone with meaningful body-fat stores may be able to supply more internally and can sometimes gain muscle around maintenance calories or during a deficit when resistance training and protein intake are appropriate. [3–5,31]

Actual food requirements can also be higher than the tissue estimate because a real muscle-gain phase includes training expenditure, changes in daily movement, repair, connective-tissue remodelling, wider adaptations and errors in estimating intake or maintenance calories. [9,22,23,38]

This is why 3,481 calories is an estimated energy requirement, not a universal surplus prescription.

How does training age change the practical meaning?

The daily tissue-building demand depends partly on how quickly someone can add muscle. A beginner may add muscle relatively quickly, so more tissue is being constructed each month. An advanced lifter normally adds much less muscle over the same period, so the daily energy demand from new tissue deposition is generally smaller. [6–9,16]

This does not mean the same 3,481-calorie estimate should be divided across any timeline. The paper’s estimate includes maintenance during an 84-day accumulation period, so changing the duration also changes part of the model. The 41-calorie daily example belongs specifically to that 84-day scenario. [38]

The broader practical conclusion still holds: as the realistic rate of muscle gain slows, there is less new tissue to fund each day. Eating a larger surplus cannot force an advanced lifter to build muscle at a beginner’s rate. Once the available rate of growth is adequately supported, increasing calories is more likely to increase fat gain than overcome that biological bottleneck. [6–9]

Does this justify a 500-calorie daily surplus?

Not from the energy cost of muscle tissue alone. Five hundred additional calories per day across the paper’s 84-day example would equal 42,000 calories. The model’s central tissue-specific estimate is 3,481 calories.

This comparison does not prove that a 500-calorie surplus is never useful. Training expenditure, recovery demands, changes in daily activity, uncertainty in maintenance intake and a deliberate goal of gaining total bodyweight can justify a larger increase for some people. However, the construction of muscle tissue itself does not justify prescribing 500 extra calories automatically, and intervention research indicates that larger or faster surpluses can increase fat gain without proportionally increasing muscle growth. [6–9,38]

How certain is the estimate?

The calculation is useful, but it should not be treated as an exact biological constant:

• It is a preprint and has not yet been peer reviewed.

• The energetic cost was modelled, not directly measured in adults gaining skeletal muscle through resistance training.

• The main tissue-deposition efficiency estimate relies substantially on evidence from infants and growing animals.

• Muscle composition and energetic efficiency may vary between people and conditions.

• The 84-day accumulation period and 10% diet-induced thermogenesis value are simplifying assumptions.

• The model does not fully capture training expenditure, wider recovery demands or every systemic adaptation. [38]

How should you apply this?

Use the model to understand the likely scale of the tissue-building cost, not to calculate an exact surplus:

• A lean or underweight person trying to gain muscle and bodyweight relatively quickly has a stronger case for a deliberate surplus.

• A newer lifter with meaningful body-fat stores may be able to build muscle around maintenance or during a modest deficit.

• An advanced lifter at a healthy body-fat level may only need maintenance calories or a small surplus because their realistic rate of muscle gain is slower. [3–9,16]

Choose a starting intake using current maintenance, training age, body composition, activity level and whether gaining bodyweight is useful. Review average bodyweight, waist measurements or progress photos, training performance and recovery across approximately three to four weeks. If the trend gives you a reason to change, adjust by roughly 100–200 calories per day and reassess.

The clearest takeaway is that approximately 3,481 calories represents the modelled total energy associated with building the kilogram, not the surplus every person must eat. The required food increase is individual, and muscle tissue alone does not justify an automatic large surplus.

How much does new muscle increase maintenance calories?

Skeletal muscle is metabolically active, but its resting requirement is modest.

Organ-and-tissue models estimate the resting metabolic rate of skeletal muscle at approximately 13 calories per kilogram per day. [13]

Under that model:

• 1 kg of additional muscle contributes roughly 13 resting calories per day;

• 3 kg contributes roughly 39;

• 5 kg contributes roughly 65.

Total daily energy expenditure may increase by more than this because a heavier person expends more energy during movement, may complete more training work, consumes more food and may alter spontaneous activity. Those changes become part of the person’s new maintenance requirement. [9,22,23]

The direct resting effect of muscle itself, however, is not 50–100 calories per kilogram per day.

This explains why an intake that was once a surplus can gradually become maintenance. If 2,700 calories initially causes slow weight gain, changes in body mass, workload and activity may eventually make 2,700 close to the person’s new maintenance intake.

You do not need to keep adding a fresh surplus on top simply because maintenance has risen.

How quickly can people realistically gain muscle?

Muscle-gain rates vary substantially with:

• effective training experience and proximity to a person’s current muscular ceiling;

• individual biological responsiveness, including genetic factors;

• programme quality;

• energy and protein intake;

• adherence;

• and whether someone is building new tissue or regaining muscle they previously held. [1,14–18]

They also generally decline as a lifting career progresses.

Biological sex does not appear to meaningfully change the relative percentage rate of hypertrophy. A 2025 meta-analysis found that males gained slightly more muscle in absolute terms, but proportional increases from baseline were similar between males and females. Because males generally begin with more muscle mass, the same relative increase can still represent more kilograms of muscle. [18]

Body size works similarly as a way of expressing the outcome: a larger person may add more kilograms from the same percentage increase. Body size alone is not well established as a cause of faster relative hypertrophy. Starting muscularity is also better understood as part of someone’s training status and proximity to their developed potential rather than as a separate standalone predictor. [16,18]

Short-term research in newer lifters

A 2020 meta-analysis by Benito and colleagues examined whole-body growth following resistance training in healthy adult men. Across 61 studies reporting fat-free mass, the pooled increase was approximately 1.53 kg over programmes averaging about ten weeks. Most participants were untrained or lightly trained. [14]

Trexler used these data in his 2025 MASS article to propose rough 12-week reference points for early-career lifters:

• approximately 0.5 kg of fat-free mass for a relatively low response;

• approximately 1.5 kg for a typical response;

• approximately 3 kg for a high response. [15]

These are expert heuristics based partly on the distribution of study means. They are not clean estimates of individual biological limits.

More importantly:

Fat-free mass is not the same as skeletal muscle.

Fat-free mass includes:

• skeletal muscle;

• water;

• glycogen;

• organs;

• bone;

• connective tissue;

• and other non-fat material. [14,27]

Starting resistance training can increase glycogen and intramuscular water. A 1.5 kg increase in fat-free mass therefore does not prove that 1.5 kg of new contractile muscle was created. [26,27]

Long-term expectations

Trexler also presented a theoretical long-term model for a typical male responder:

• year one: approximately 4 kg of fat-free mass;

• year two: approximately 2.4 kg;

• year three: approximately 1.4 kg;

• year four: approximately 0.9 kg;

• later years: less than 0.5 kg annually. [15]

The model deliberately assumes that progress falls by approximately 40% each year. It is not the observed trajectory of a cohort followed for ten years.

Its value is expectation-setting, not prediction.

The broader point is credible: drug-free lifters generally have more growth potential early in their training careers, with diminishing returns as muscularity and effective training experience accumulate. A newer expert review similarly recommends relatively modest intentional weight-gain rates of approximately 0.1–0.25% of bodyweight per week rather than an aggressive universal bulk. [16]

Real progress will not follow a perfectly smooth curve. Injuries, poor training blocks, improved programming, changes in adherence and periods of detraining can produce plateaus and renewed progress.

Returning lifters are a special case

A detrained lifter may regain previously held muscle and strength faster than an equally advanced continuously trained lifter can create entirely new tissue.

In a 2024 study, periodic training with a ten-week detraining period produced rapid regain during retraining, leading to broadly similar final muscle-size and strength outcomes to continuous training. [17]

That does not mean all previous tissue returns immediately. It does mean that “advanced” is not a complete description of someone returning substantially below their previous level.

How training status and body composition change the recommendation

Training status alone does not determine whether someone should use a deficit, maintenance or a surplus. The decision also depends on current body-fat level, bodyweight, whether total weight needs to increase, and whether the immediate priority is fat loss, recomposition or muscle gain.

There is no experimentally proven set of beginner, intermediate and advanced weight-gain rates. The following ranges combine direct surplus evidence, current expert synthesis and practical coaching judgement. The weight-gain ranges apply only when the person is deliberately trying to gain bodyweight. [6–8,16]

Example: for a 75 kg lifter, 0.1% of bodyweight per week = 75 g/week, and 0.25% per week = about 190 g/week.

The broad 0.1–0.25% range is supported as an expert synthesis. The narrower category-specific ranges are coaching heuristics. No trial has shown that 0.08% per week is superior to 0.12% for an advanced lifter. [16]

Training status should be judged by productive training history rather than years of gym membership. Someone with three years of nominal experience may have completed only six months of consistent, progressive training.

Someone relatively new and carrying moderate or higher body fat

This person is a strong candidate for maintenance or a moderate deficit, depending on whether stable bodyweight or fat loss is the priority.

They have:

• a relatively novel training stimulus;

• stored body energy;

• and substantial room to improve programme quality and skill.

A deliberate surplus may increase fat gain without being necessary to begin building muscle. [3–5]

A lean or underweight beginner

This person has comparatively high muscle-gain potential and may also need to increase total bodyweight. A purposeful surplus is therefore more defensible than it would be for a beginner already carrying substantial body fat.

A small-to-moderate surplus may reduce the chance that food intake limits training or rapid early adaptation. A somewhat larger surplus may be reasonable when the person is clearly underweight or chronically under-fuelled. This is a practical inference from growth potential and weight-restoration needs, not proof that a larger surplus directly produces more muscle. [6–9,16]

An advanced lifter at a reasonable body-fat level

Maintenance may be a viable strategy, particularly when training performance, recovery and protein intake are adequate and the lifter is content with slow progress.

Because the amount of new tissue an advanced lifter can add is usually small, the modelled energy required to deposit that tissue would also be small. That does not prove maintenance and a tiny surplus are equivalent, because tissue-level calculations do not fully capture training expenditure, protein turnover, recovery or energy availability. Forcing a visible weekly rate of scale gain can nevertheless readily outpace hypertrophy.

The uncertainty matters: we do not have long-term trials showing that maintenance and a small surplus produce identical results in advanced lifters. A very small surplus may provide a useful buffer against under-eating, but advanced status alone is not evidence that a larger surplus is required. [6,8,9,16]

Someone underweight

Body recomposition cannot indefinitely move someone from 60 kg to a desired muscular bodyweight of 70–72 kg while body fat keeps falling.

Over the complete process, substantial net bodyweight gain requires sustained periods in which energy intake exceeds expenditure.

This person may reasonably accept a faster rate of gain and a less favourable muscle-to-fat ratio than an advanced lifter whose bodyweight is already appropriate.

Someone excessively lean or under-fuelled

Being lean is not automatically unhealthy, and there is no universal body-fat percentage at which muscle growth stops.

However, prolonged low energy availability can affect reproductive function, bone health, metabolic function, mood, recovery and performance. Natural-bodybuilding case evidence also shows that extreme contest-level leanness can be accompanied by substantial physiological disruption and a prolonged recovery period. [29,30]

Controlled short-term studies provide direct mechanistic support for concern about under-fuelling. Ten days of low energy availability reduced integrated myofibrillar and sarcoplasmic muscle protein synthesis in trained women, while five days of energy restriction reduced resting muscle protein synthesis in men and women. Resistance exercise and protein improved the acute response, but these studies were short and did not measure long-term hypertrophy. They support avoiding chronic under-fuelling; they do not define a precise surplus that maximises growth. [33,34]

Relevant warning signs can include:

• persistent hunger or food preoccupation;

• declining training performance;

• unusual fatigue;

• poor recovery;

• menstrual disturbance;

• reduced libido;

• and recurrent bone stress problems. [29]

In that situation, restoring adequate energy availability may be more important than engineering the smallest possible surplus. Individual assessment by an appropriately qualified sports dietitian or doctor may also be warranted.

How to estimate maintenance calories

A calorie calculator can provide a starting estimate. It does not measure your true maintenance requirement.

A more useful free-living estimate comes from comparing:

• what you are consistently eating;

• with what your average bodyweight is consistently doing.

A practical maintenance-estimation process

For at least two weeks, and preferably three or more:

• Continue eating roughly as you normally do.

• Track food intake using a consistent method.

• Weigh yourself most mornings.

• Weigh after using the toilet and before food or drink.

• Use similar clothing conditions.

• Calculate each week’s average bodyweight.

• Compare several weekly averages and the overall direction.

If average bodyweight is broadly stable, average intake is probably close to maintenance.

If weight is consistently rising, intake is probably above current maintenance.

If weight is consistently falling, intake is probably below it.

If you have remained around the same bodyweight for several months, your habitual average intake is already close enough to maintenance for practical purposes, even if you have never calculated the number precisely.

Worked maintenance example

Assume a lifter tracks an average of 2,650 calories per day.

Week 1

Daily morning weights:

80.0, 80.2, 79.9, 80.1, 80.0, 80.3, 80.0 kg

Weekly average:

560.5 ÷ 7 = 80.07 kg

Week 2

80.1, 80.3, 80.0, 80.2, 80.1, 80.2, 80.1 kg

Weekly average:

561.0 ÷ 7 = 80.14 kg

Week 3

80.2, 80.1, 80.3, 80.0, 80.2, 80.1, 80.2 kg

Weekly average:

561.1 ÷ 7 = 80.16 kg

Across three weeks, average bodyweight moved from 80.07 to 80.16 kg while average intake was 2,650 calories.

That is close enough to treat approximately 2,650 calories as a useful working estimate of maintenance.

It is not proof that true expenditure equals exactly 2,650 every day.

For an intermediate lifter prioritising size, an initial test might be:

2,650 × 1.05 = 2,782.5 calories

In practice, that could be rounded to approximately 2,800 calories per day.

The lifter would then maintain that intake for around three to four weeks and assess the trend.

Does a 100 g difference prove maintenance?

No.

A difference of 100 g between two weekly averages is not a validated stability threshold.

Bodyweight can change because of:

• hydration;

• sodium intake;

• carbohydrate and glycogen;

• bowel contents;

• unusually large meals;

• inflammation following unfamiliar training;

• and the menstrual cycle.

Research on menstrual-cycle variation has found an average bodyweight difference of approximately 0.45–0.5 kg across phases, largely associated with extracellular fluid. [24]

Two weeks can give you a starting estimate. Three to six weeks under reasonably consistent conditions provide a stronger signal, particularly when the intended gain rate is very slow.

Can you calculate the surplus from weight change?

The common rule that 1 kg of weight change equals 7,700 calories is only an approximation.

Suppose someone gains 0.5 kg over four weeks:

0.5 × 7,700 = 3,850 calories

3,850 ÷ 28 = approximately 138 calories per day

This suggests an average surplus of roughly 140 calories per day.

It is useful as a ballpark, not a physiological measurement.

Bodyweight change can include:

• fat;

• muscle and other lean tissue;

• glycogen;

• water;

• and gastrointestinal contents.

Energy expenditure also changes as intake and bodyweight change. Dynamic weight-change models were developed because a static calorie-per-kilogram rule becomes increasingly inaccurate over time. [22]

Use the calculation to orient yourself. Use the observed multi-week trend to make decisions.

How many extra calories should you eat to gain muscle?

There is no universally correct calorie number.

A practical framework is:

These are coaching starting ranges. They are not experimentally proven thresholds.

For a maintenance intake of 2,500 calories:

• 5% is 125 calories;

• 10% is 250 calories;

• 15% is 375 calories.

For many ordinary gaining phases, this produces an initial increase of roughly 100–300 calories per day rather than an automatic 500 calories or more.

A larger surplus may be reasonable for a highly active, lean or underweight beginner whose goal includes substantial bodyweight gain. It is harder to justify as the default for an advanced 80 kg lifter whose realistic annual muscle gain may be small.

The resulting trend matters more than the intended arithmetic.

Is a 500-calorie surplus too much?

It can be. A 500-calorie daily surplus is not automatically inappropriate, but it is more aggressive than many natural lifters need. It may be reasonable for someone lean or underweight who is deliberately prioritising faster total bodyweight gain. For an intermediate or advanced lifter trying to limit fat gain, a smaller starting surplus is usually easier to justify. [6–9,16]

Conservative versus more aggressive gaining

A conservative approach generally suits someone who:

• is intermediate or advanced;

• is already at an appropriate bodyweight;

• strongly prefers remaining lean;

• wants to minimise future dieting;

• and is comfortable accepting that progress may be difficult to detect over short periods.

A somewhat more aggressive approach may suit someone who:

• is a lean beginner with high muscle-gain potential;

• is underweight;

• needs to increase total bodyweight substantially;

• is recovering from an excessively lean or chronically under-fuelled state;

• or is more concerned about under-eating than gaining some additional fat.

A more aggressive approach reduces the chance of under-eating, but it does not guarantee more muscle.

Gaining no fat at all may be unrealistic during a prolonged gaining phase. Gaining substantially more fat than muscle is not a requirement.

Why very small surpluses are difficult to measure

Maintenance calories are not one fixed daily number. They are better understood as a moving range or a multi-week average.

Your expenditure can change from day to day depending on:

• whether and how much you trained;

• steps and other spontaneous movement;

• how physically demanding work or daily life was;

• food intake and the energy used to digest it;

• bodyweight;

• and normal biological variation. [9,22,23]

Food labels, portion sizes, restaurant meals and cooking methods also introduce error.

That makes a target such as an exact 50-calorie daily surplus falsely precise. You cannot reliably know that maintenance was exactly 2,650 calories yesterday or that you finished the day exactly 50 calories above it.

This does not make calorie tracking useless, and it does not mean you need to become obsessive about the numbers.

Treat maintenance and the intended surplus as workable ranges. Use a repeatable tracking method, then let several weeks of bodyweight, waist and gym-performance data show whether the range is appropriate.

Want help making the most of your gaining phase? SPC Performance Lab offers in-person and online coaching to help you structure your training and nutrition to optimise your progress. View the coaching options.

Protein intake during a gaining phase

Protein does not operate through a sharp on-off threshold.

People can gain muscle while consuming less than 1.6 g/kg/day. Increasing protein intake generally appears to improve lean-mass or muscle-gain outcomes on average, but the extra benefit becomes progressively smaller as intake rises. [19–21]

Morton and colleagues analysed 49 resistance-training trials involving 1,863 participants. Protein supplementation produced small additional gains in fat-free mass, muscle size and strength. Their breakpoint analysis estimated that the average relationship between total protein intake and additional fat-free-mass gain levelled off at approximately 1.62 g/kg/day, but the confidence interval around that estimate extended from approximately 1.03 to 2.20 g/kg/day. [19]

That 1.62 figure is not a minimum below which muscle growth stops, and it is not a precise ceiling for every individual.

Other meta-analyses support the same general pattern. Nunes and colleagues concluded that increasing daily protein intake produces small additional gains in lean body mass, particularly when combined with resistance training. Tagawa and colleagues found a dose-response relationship across a wide intake range, but the marginal benefit diminished as protein intake increased. These analyses mainly measured lean or fat-free mass rather than newly synthesised skeletal muscle, and the included populations and interventions varied. [20,21]

For most lifters gaining muscle:

• Around 1.6 g/kg/day is a strong evidence-based target that is likely to capture most of the average benefit.

• Around 1.8–2.0 g/kg/day is a simple practical target that provides some margin for tracking error and day-to-day variation.

• Up to approximately 2.2 g/kg/day may provide a small additional benefit or useful margin for some people, but it is not automatically necessary.

• Below 1.6 g/kg/day can still support muscle gain; it simply may not capture the full average benefit shown in the research.

For an 80 kg lifter:

• 1.6 g/kg = 128 g/day;

• 2.0 g/kg = 160 g/day;

• 2.2 g/kg = 176 g/day.

There is little evidence that routinely pushing well beyond approximately 2.2 g/kg/day produces further hypertrophy when total energy intake is adequate. Very high protein intake may also leave less room for carbohydrate and dietary fat. Adequate carbohydrate can help support repeated high-intensity resistance training, although no single carbohydrate target applies to every lifter. [9,16,19–21]

How quickly should you gain weight when building muscle?

A recent expert review recommends approximately 0.1–0.25% of bodyweight per week as a broad intentional gain range for drug-free athletes. [16]

For an 80 kg person:

• 0.1% = 80 g per week;

• 0.25% = 200 g per week.

That is approximately 0.35–0.87 kg per month.

The upper end makes more sense for:

• a lean beginner with substantial muscle-gain potential;

• an underweight person;

• or someone deliberately prioritising faster total bodyweight gain.

The lower end, or even near-maintenance bodyweight, makes more sense for an advanced natural lifter whose expected muscle-gain rate is very slow.

Why 0.25–0.5% per week may be too fast

At 80 kg:

• 0.25% = 200 g per week;

• 0.5% = 400 g per week.

A gain of 400 g per week is approximately 1.7 kg per month.

That may be acceptable when total bodyweight gain is itself an important goal. It is difficult to reconcile with the realistic muscle-gain potential of an advanced natural lifter.

The direct surplus studies provide much stronger evidence that faster gain increases fat than that it proportionately increases hypertrophy. [6,7]

How do you know whether the weight is muscle or fat?

You cannot know perfectly.

There is no convenient free-living method that tells a gym member exactly how many grams of contractile skeletal muscle were added in a month.

The best approach is to combine several imperfect measures.

Why lean mass is not the same as new muscle

Many gaining studies report changes in lean mass or fat-free mass from DXA or BIA. These measurements include water, glycogen, organs and other non-fat tissues; they do not directly measure newly built skeletal-muscle protein. Controlled studies show that changing hydration, muscle glycogen or creatine can shift DXA lean-tissue estimates by roughly 1–3 kg without an equivalent amount of new muscle. This is especially important in short studies where carbohydrate intake, sodium, creatine use or scan preparation changes. [26–28,35]

Ultrasound and MRI are more muscle-specific, but ultrasound measures selected regions and small changes can still sit close to measurement error. The most defensible interpretation combines standardised body-composition testing with strength, circumferences, training performance and longer-term trends. [36,37]

Bodyweight averages

Weigh frequently enough to create weekly averages.

A rising average confirms that total body mass is increasing. It does not identify what the gain consists of.

Judge the trend over several weeks rather than reacting to individual mornings.

Progress photographs

Take relaxed front, side and back photographs under similar conditions:

• same lighting;

• same room;

• same distance and camera position;

• similar time of day;

• similar hydration and meal conditions where practical.

Fortnightly or monthly comparisons are generally enough. Advanced lifters may require several months before meaningful visual changes become obvious.

Gym performance

Ask whether performance is trending upwards across several hypertrophy-relevant exercises and repetition ranges.

Useful signs include:

• performing more repetitions with the same load;

• lifting more weight for a similar number of repetitions;

• completing the same weight and repetitions at a lower RPE or with more repetitions in reserve;

• or tolerating more productive training volume without a disproportionate increase in fatigue.

Improved performance supports the inference that training is productive, but it does not prove that muscle has been gained. Technique, exercise skill, confidence and neural adaptations can improve performance without an equivalent increase in muscle size. One-repetition maximum strength can also change differently from hypertrophy. [3,25]

Conversely, muscle may grow without an immediate improvement in one-repetition maximum strength.

Sustained improvement across several exercises, combined with sensible changes in bodyweight, waist measurements and photographs, strengthens the inference that useful adaptation is occurring.

Circumference measurements

Useful sites include:

• waist;

• upper arm;

• thigh;

• chest;

• hips or glutes.

A rapidly expanding waist with little change in limb measurements, photographs or training performance is a warning that a high proportion of the gain may be fat.

Limb measurements are also affected by body fat, glycogen, hydration and measurement technique, so they should not be used alone.

Training and recovery

Productive sessions, tolerable fatigue and adequate recovery provide useful supporting information.

Poor recovery, persistent hunger and declining performance may suggest inadequate intake, but none directly measures hypertrophy. Similar symptoms can also result from poor sleep, excessive training, psychological stress or illness.

How and when should calories be adjusted?

Do not change calories because one weekly average behaves unexpectedly.

For most lifters, hold a new intake for approximately two to four weeks, with longer observation often appropriate when the intended rate is very slow.

A practical adjustment is usually:

• approximately 100–200 calories per day;

• or roughly 3–5% of current intake.

These are coaching heuristics, not experimentally proven adjustment sizes. They are generally large enough to affect the trend without creating a major overcorrection.

Monitoring and adjustment guide

An earlier change is sensible when the signal is unmistakable. An 80 kg lifter unexpectedly gaining 1 kg per week while their waist rises rapidly does not need another month of evidence.

The opposite also applies. An advanced lifter should not add calories because their weekly average fell 200 g after a low-sodium day.

When should you maintain, cut or stop gaining?

There is no reliable rule such as always bulking from exactly 10% to 15% body fat.

Body-fat measurements are imprecise, and the appropriate decision depends on: [27,28]

• health;

• performance;

• waist measurements;

• appearance;

• personal preference;

• and whether continued weight gain serves the goal.

Move to maintenance when

Maintenance may be appropriate when:

• you are happy with your current body composition;

• you want to keep bodyweight broadly stable rather than deliberately gain or lose weight;

• training is still progressing;

• or deliberate weight gain is no longer necessary.

Stopping the surplus does not mean muscle growth must immediately stop. Maintenance can support hypertrophy in at least some circumstances. [5,6,8]

For an advanced lifter whose potential muscle-gain rate is extremely slow, a long maintenance phase may be more rational than forcing a clearly visible weekly scale increase.

Use a cut when

A fat-loss phase may make sense when:

• accumulated body fat no longer suits your preference;

• waist gain is becoming disproportionate;

• you would rather become leaner before gaining again;

• or continuing the surplus would create substantially more dieting work later.

Resistance training and adequate protein improve lean-mass retention during a deficit. [31,32]

In resistance-trained athletes, Mettler and colleagues found that higher protein intake reduced lean-body-mass loss during a short, substantial weight-loss phase. [31]

Garthe and colleagues found more favourable lean-mass and performance outcomes with a slower weight-loss target than with a faster one in elite athletes. [32]

A short mini-cut can therefore be a useful scheduling tool. It is not a special physiological method that guarantees preservation of every gram of muscle.

Leaner and more advanced lifters generally have less room for error with severe deficits. [3,29]

Will a slower gainer eventually reach the same muscular endpoint?

Possibly, but this has not been proven.

Short-term studies give us reason to think that once intake is broadly adequate, making bodyweight increase much faster can add substantially more fat without creating a proportional increase in muscle. [6–8]

From that, it is reasonable to infer that a conservative gainer may sometimes accumulate similar muscle over a longer period while adding less excess fat.

However:

• no multi-year randomised trial has compared maintenance and different modest surplus strategies to their final muscular endpoint;

• intake that is too low may limit someone whose energy availability, recovery or training performance is compromised;

• differences too small to detect over eight weeks could matter over several years;

• and individual responses vary. [3,6–9,16]

The practical conclusion is not that every adequate intake eventually produces the same result.

It is that there is little justification for assuming the fastest scale gain produces the best long-term muscular outcome.

Practical decision guide

1. Estimate maintenance. Track average intake and morning bodyweight for at least two weeks, preferably three or more.

2. Choose the energy strategy from the whole context.

   • A beginner carrying more body fat and prioritising fat loss may use a moderate deficit.

   • Maintenance may suit a beginner aiming for body recomposition, a returning lifter or an advanced lifter who wants stable bodyweight and accepts slow progress.

   • A small surplus may suit a lean intermediate or advanced lifter prioritising muscle gain.

   • A more purposeful surplus may suit a lean or underweight beginner, or someone recovering from chronic under-fuelling.

3. Choose a conservative starting target.

   • For many deliberate gaining phases, begin around 2–10% above estimated maintenance depending on training status, body composition and goal.

   • This often means approximately 100–300 extra calories per day.

   • Use larger amounts selectively rather than by default.

4. Keep protein adequate.

   • Around 1.6 g/kg/day is a strong general target, not a hard minimum.

   • Around 1.8–2.0 g/kg/day is an easy practical target.

   • Up to approximately 2.2 g/kg/day may provide a small additional margin for some lifters.

5. Monitor several indicators together.

   • Weekly average bodyweight

   • Waist and other circumferences

   • Progress photographs

   • Performance across multiple exercises

   • General training and recovery

6. Give small changes enough time.

   • Usually two to four weeks

   • Longer when the intended gain rate is extremely slow

7. Adjust modestly.

   • Add or remove approximately 100–200 calories per day

   • Reassess rather than making repeated rapid changes

8. Stop gaining when it no longer serves the goal.

   • Maintain when you want stable bodyweight and training is productive

   • Cut when accumulated fat justifies it

   • Do not wait for an arbitrary body-fat percentage

Final takeaway

You do not need to eat 500 calories or more above maintenance every day simply because your goal is building muscle.

Resistance training creates the primary hypertrophic stimulus. Protein supplies the amino acids required for growth and remodelling. Adequate energy supports training, recovery and tissue synthesis.

A calorie surplus can be useful, especially for someone who is lean, underweight, under-fuelled or deliberately trying to gain substantial bodyweight. But it is not universally required, and larger surpluses produce a much clearer increase in fat gain than in measured hypertrophy.

Training status changes the recommendation, but not in the simplistic direction often assumed. A beginner can appropriately use a deficit, maintenance or a surplus depending on body fat and goals. A lean or underweight beginner may justify a larger surplus because muscle-gain potential and total weight-gain needs are greater. An advanced lifter at a reasonable body-fat level may be able to progress at maintenance or with a very small surplus because realistic muscle gain is slow. Direct long-term evidence comparing those exact strategies remains limited.

An August 2026 preprint estimated a central total food-energy equivalent of approximately 3,481 calories for building 1 kg of wet skeletal muscle. Approximately 2,126 calories are expended while synthesising, depositing and maintaining the tissue and processing the extra food, while approximately 1,355 calories remain stored in the completed muscle. This is an estimate of the energy associated with constructing the tissue, not the calorie surplus every person must eat. Some of the energy can come from existing body stores, while real food requirements can be higher when training, recovery, activity and tracking uncertainty are considered. As the realistic rate of muscle gain slows with training experience, the daily tissue-building demand generally becomes smaller. Use current intake, training age, body composition and several weeks of real progress to choose and adjust the smallest intake increase that supports useful muscle gain without unnecessary fat gain. [3–9,16,22,23,38]

For most natural lifters, the most defensible approach is to:

• choose maintenance, a deficit or a surplus according to training status, body composition and the immediate goal;

• start conservatively when deliberately gaining;

• keep protein intake adequate;

• monitor several indicators;

• and adjust from several weeks of observed results.

The target is not the largest surplus you can tolerate.

It is enough food to support productive training and muscle growth without accumulating substantially more fat than the goal requires.

Related SPC guides: How to calculate maintenance calories and macros and Should you bulk or cut?

Want help applying this to your training and nutrition program to optimise your progress? SPC Performance Lab offers in-person, online and monthly coaching with structured programming, nutrition guidance and ongoing adjustments. View the coaching options or book a free consult for a no-pressure chat to see if we can help you.

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