How Many Calories to Build Muscle?

By Jesse · Last updated August 20, 2026

The short answer is maintenance plus 10 to 15%. The interesting answer is why it is not more, because the intuition that more food means more muscle is both universal and wrong. Muscle is built at a rate set by training and recovery, not by intake, and calories beyond that ceiling are stored the only other way your body knows how.

This is the guide that owns the size of the surplus. How to establish the maintenance figure it is built on — and why the estimate needs calibrating — is covered in why TDEE calculators are estimates. How much protein to eat alongside it is in how much protein you really need per day.

Step one: find maintenance, then add to it

A surplus is defined relative to your maintenance calories, so that figure has to come first. For the reference body used throughout this guide — a 28-year-old man, 178 cm, 75 kg, training four times a week — the TDEE calculator puts resting energy at 1,728 kcal and maintenance at about 2,678 kcal a day.

Two cautions before adding anything. First, that maintenance number is an estimate with a margin of several hundred calories, so a small surplus on paper can be no surplus at all in reality, or a large one. Second, maintenance rises as you gain weight, which means a fixed intake becomes a shrinking surplus over a few months. Both problems have the same solution: treat the number as a starting hypothesis and let three weeks of weight data correct it.

What the arithmetic says a surplus buys

Energy balance gives a straightforward prediction. Body tissue stores roughly 7,700 kcal per kilogram, so a daily surplus multiplied by seven and divided by that figure gives an expected weekly weight gain.

Now read the last column as a muscle-gain claim, and it collapses. Nobody builds 7.6 kg of muscle in 12 weeks. Even in trials designed to maximise it, lean mass gains arrive in single kilograms over months. So a +700 kcal surplus is not a plan to build 7.6 kg of muscle; it is a plan to build whatever muscle you were going to build anyway and carry several kilograms of fat on top of it.

A +300 kcal surplus predicts 0.27 kg a week, which is a rate a well-trained person can plausibly fill with a respectable fraction of lean tissue. That is the reasoning behind the modest figure our macro calculator uses for its muscle-gain setting.

What happened when researchers tested a bigger surplus

This is not only a theoretical argument. A randomised trial followed 39 elite athletes through an 8- to 12-week weight-gain phase, all of them adding four strength-training sessions a week to their normal sport training. One group received a meal plan engineered to produce a surplus. The other simply ate as they chose.

The counselled group ate about 621 kcal a day more, gained about 1.6 kg more body weight, and put on five times as much fat. Both groups gained lean body mass, and the amount they gained was no different between them. The extra energy showed up as fat.

Expressed as a weekly rate, the group that ate as it chose gained about 0.15% of body weight a week over the intervention, and the counselled group about 0.39%. The slower of those two rates bought the same lean mass with roughly a fifth of the fat gain. That is the empirical basis for the 0.1 to 0.25% a week target further down this page, rather than a rule of thumb someone invented.

Three honest caveats. These were young elite athletes, who may respond differently from a recreational lifter. Intake in the ad libitum group was self-reported with a wide spread, so the 621 kcal gap is approximate. And a study of this size cannot rule out a small lean-mass advantage it lacked the power to detect. What it does establish is that a large surplus is not a reliable route to more muscle, which is the claim most bulking advice depends on.

Worth noticing too: the arithmetic in the previous section over-predicts what happened here. A 621 kcal daily difference sustained over 10 weeks predicts about 5.6 kg of extra body weight. The trial measured 1.6 kg — roughly a 3-fold over-prediction. That is a rough comparison, since the groups differed in starting weight and one intake figure was self-reported, but the direction is the familiar one: energy-balance sums over-predict over-predict in the real world, for the same reasons they do during weight loss — reporting error, and expenditure that moves when intake moves. We quantified that effect for fat loss in how far the linear weight-loss model drifts.

Why the textbook calculation is not trustworthy

A common way to size a surplus is to work out the energy stored in the muscle you want to add and eat that much extra. A 2019 review in Frontiers in Nutritionexamined that reasoning directly and found it wanting on several counts. Estimates built only on the energy content of the tissue ignore the metabolic cost of building it, the acute adjustments the body makes when intake rises, and the effect of training experience and current energy status. The review's summary is blunt: the specific surplus required to facilitate hypertrophy is unknown, published guidance ranges broadly as a result, and none of the estimates has been validated in a resistance-training population.

That is a genuinely useful conclusion, not a shrug. If nobody can calculate the correct surplus from first principles, then confidently precise recommendations should be distrusted, and the sensible strategy is to start small and let measurement do the work. The cost of being slightly too low is a few weeks of slower gain. The cost of being much too high is months of fat to remove afterwards.

When you do not need a surplus at all

A surplus makes gaining muscle easier; it is not a precondition. Three groups regularly add lean mass without one:

• Beginners. The first months of resistance training produce the fastest gains anyone ever gets, and they happen at maintenance without difficulty. Adding a surplus at this stage mostly adds fat to an already favourable situation.
• People with fat to lose. Stored energy is available energy. A trial of young men in a 40% energy deficit, eating 2.4 g of protein per kilogram and training six days a week, gained 1.2 kg of lean mass in four weeks while losing 4.8 kg of fat — the control group on 1.2 g/kg gained 0.1 kg of lean mass and lost 3.5 kg of fat. High protein and hard training, not a surplus, did that.
• Anyone returning after a break. Regaining previously held muscle is much faster than building it the first time, and does not require extra calories to happen.

The people who genuinely need a surplus are trained, already lean, and past the phase where novelty does the work. If that is not you yet, the more efficient plan may be to eat at maintenance, train properly, and revisit the question in six months.

Setting your own number

1. Estimate maintenance with the TDEE calculator, choosing the lower activity level if you are between two.
2. Add 10 to 15% — for this reference body, 268 to 402 kcal, giving 2,946 to 3,080 kcal a day. Round to something you can actually hit.
3. Set protein first inside that total. Roughly 1.6 to 2.2 g per kilogram of body weight, from the protein calculator. Carbohydrate and fat divide the remainder to taste; carbohydrate usually deserves the larger share when training volume is high.
4. Hold it for three to four weeks and record body weight most mornings plus the load and reps on two or three main lifts.
5. Compare seven-day average weights and adjust once. Aim for roughly 0.1 to 0.25% of body weight per week — about 0.07 to 0.19 kg a week at 75 kg. Flat for three weeks, add 100 to 200 kcal. Faster than that with no progress on the bar, remove 100 to 200 kcal.

Note what is being judged. Scale weight tells you whether the surplus exists; the training log tells you whether it is being used. Weight up and lifts up is the surplus working. Weight up and lifts flat means the extra food is going somewhere you did not intend, and the fix is usually in the programme rather than the kitchen. To see how much of the gain is fat, the body fat calculator tracked monthly with a tape measure is crude but directionally honest, and a waist measurement climbing faster than your lifts is the clearest signal to cut the surplus back.

Common questions

These are general estimates for healthy adults, not medical advice. If you are pregnant, under 18, have a medical condition, or a history of disordered eating, talk to a doctor or registered dietitian before changing your intake. See our methodology for the sources behind these figures.