Calorie Surplus Calculator
By Rick Campbell · Updated · Sourced to primary literature · Not medical advice
A calorie surplus is eating above the energy you burn. It is the condition under which the body will add tissue, and it is the reason a lifter who trains hard on maintenance calories often stays exactly the same weight for a year. This calculator estimates your maintenance calories from height, weight, age, sex and activity, then adds a surplus sized to a weekly rate of gain you choose.
What it will not do is size that surplus to enthusiasm. The weekly rate is capped at 0.5% of bodyweight, the surplus at 20% above maintenance, and a goal weight above a BMI of 27.5 for your height is refused, because past that point describing the extra kilograms as lean gain stops being accurate. Those limits are written into the calculation, not into the advice around it.
The page also shows what most surplus calculators leave out: how fast muscle can actually be added at your training age, the protein intake that decides how much of the gain is lean tissue, and a straight account of where the rest of the surplus goes. A calorie target is the easy half of the problem. Knowing what the number can and cannot buy is the half that matters.
In brief
- A surplus of roughly 10–20% above maintenance calories is enough to support muscle growth; larger surpluses add fat rather than speeding the process.
- Weekly gain of about 0.25–0.5% of bodyweight is the rate the evidence supports for adding mostly lean tissue, and this calculator caps the plan there.
- Muscle is gained fastest in the first year of consistent resistance training and progressively more slowly after that, so the same surplus yields less muscle every year.
- Protein at 1.6–2.2 g per kilogram of bodyweight is the intake range beyond which resistance-training gains stop improving with more.
- Without resistance training a surplus is simply weight gain: the calories arrive, but nothing signals the body to build tissue with them.
Calculator
What you'll see here
Your daily calorie target with the surplus it puts over maintenance, the weekly rate it works out to as a percentage of your bodyweight, a protein target in grams, how many weeks the plan runs if you add a goal weight, and a plain account of how much of the gain is likely to be muscle.
| Training experience | Approximate gain per month | Roughly, for an 80 kg lifter |
|---|---|---|
| First year of consistent training | 1 – 1.5% of bodyweight | 0.8 – 1.2 kg a month |
| Second year | 0.5 – 1% of bodyweight | 0.4 – 0.8 kg a month |
| Third year and beyond | 0.25 – 0.5% of bodyweight, often less | 0.2 – 0.4 kg a month |
These are approximate ranges in wide practical use among strength coaches, not a published regression: no trial has measured them precisely, and individual rates vary a great deal. Women typically gain in similar proportions but from a smaller absolute base, so the percentage column travels better than the kilograms column. Read them as a ceiling on what a surplus can be converted into, not as a target to hit.
| Rail | Limit | Why it is there |
|---|---|---|
| Weekly gain rate | 0.5% of bodyweight a week | Faster gain adds a rising share of fat, not muscle |
| Daily surplus | 20% above maintenance | A bigger surplus does not build muscle any faster |
| Goal weight | BMI 27.5 for your height | Past that, calling the gain lean stops being honest |
| Protein | 1.6 – 2.2 g per kg of bodyweight | The range where training gains stop improving with more |
There is no aggressive mode and no way to switch these off. Planning for 7,700 kcal per kilogram is a long-run approximation borrowed from the weight-loss literature; applied to gaining, it assumes the tissue you add resembles ordinary bodyweight rather than pure muscle, which is why the weekly rate is the honest number to steer by and the calorie figure is only the lever.
What a calorie surplus does and does not buy
A surplus supplies the raw material and the hormonal environment for tissue to be added. It does not decide what kind of tissue. That decision is made by the training stimulus, by protein intake, by sleep and by how long you have been lifting. Eat 500 kcal a day above maintenance while training hard in your first year and a meaningful share of what you add is muscle. Eat the same 500 kcal while doing nothing in particular and almost none of it is.
The distinction matters because the scale reports only the total. Two people gaining 0.4 kg a week can be having completely different experiences underneath: one adding a couple of hundred grams of lean tissue with the rest as fat and fluid, the other adding fat almost exclusively. The weekly number looks identical. This is why the result panel pairs the calorie target with a protein target and a training note rather than presenting the calories alone.
It is also worth being clear that a surplus is not strictly required for every gain in muscle. Untrained people, people returning after a break, and people carrying a lot of body fat can add muscle while eating at or below maintenance, because the fat they already carry supplies the energy. The review by Slater and colleagues makes this point carefully: the surplus is a helpful condition for hypertrophy, not a mechanical precondition for it.
How big the surplus should be, and why bigger is not faster
The practical range is 10–20% above maintenance calories: for most adults that is somewhere between 200 and 500 kcal a day. The lower half of that range suits experienced lifters and anyone who would rather add less fat; the upper half suits newer lifters, who can convert more of it. This calculator sizes the surplus from the weekly rate you choose and then holds it at 20% of maintenance if the arithmetic asks for more.
The reason bigger is not faster is that muscle protein synthesis has a ceiling set by the training stimulus and by recovery, and no amount of extra food raises it. Once you are eating enough to support the muscle you are capable of building this week, additional calories have exactly one destination. Garthe and colleagues showed this directly in elite athletes: a group eating a controlled surplus and a group eating ad libitum both gained lean mass at a similar rate, but the ad libitum group gained substantially more fat doing it.
There is a second, quieter cost. Fat gained during a surplus has to be lost again later, in a deficit, and a deficit is where muscle is at risk. A year spent adding four kilograms of muscle and eight of fat, then dieting the fat back off, usually finishes behind a year spent adding three of muscle and two of fat. The slower plan is not a compromise; on a twelve-month view it is normally the faster one.
Realistic rates of muscle gain by training age
Training age (how long you have been lifting consistently, not how old you are) is the single best predictor of how fast muscle can be added. In the first year of consistent resistance training, roughly 1–1.5% of bodyweight per month of muscle is a commonly cited working range. In the second year that roughly halves, and from the third year onward it falls to something like 0.25–0.5% per month or less. Women typically gain in similar proportions from a smaller absolute base, so the percentages travel better between people than the kilograms do.
These ranges are widely used practical guidance among strength coaches rather than the output of a published regression. No trial has measured the ceiling precisely, the spread between individuals is large, and anyone quoting them to two decimal places is inventing precision. They are still useful, because they tell you what a surplus can possibly be converted into. If your training age says a quarter of a kilogram of muscle a month, and the scale is moving at a kilogram a month, the difference is not a mystery.
- First year of consistent training: roughly 1–1.5% of bodyweight a month.
- Second year: roughly 0.5–1% a month.
- Third year and beyond: roughly 0.25–0.5% a month, often less.
- Returning after a long layoff behaves more like the first year than the fifth: regaining previously held muscle is markedly faster than building it the first time.
Protein and training: the levers that decide what the gain is made of
If the calorie surplus sets how much weight is added, protein and training set how much of it is muscle. The meta-analysis by Morton and colleagues pooled forty-nine studies and found that resistance-training gains in lean mass improved with protein intake up to about 1.6 g per kilogram of bodyweight per day, with the confidence interval reaching 2.2 g/kg. Above that, more protein did not produce more muscle. That is why this calculator returns 1.6–2.2 g/kg rather than a single number: the lower bound is where the benefit plateaus and the upper bound is the honest edge of the estimate.
Training is the more important of the two and the one people are vaguer about. A surplus with a progressing programme (adding weight, reps or quality sets over months) is a bulk. The same surplus with a static programme is weight gain with a gym membership attached. The programme does not need to be elaborate; it needs to get measurably harder over time, and you need to be able to point at the evidence that it has.
Sleep and total training volume fill in most of the rest. Neither is something a calculator can size for you, but both move the composition of the gain more than the difference between a 300 and a 400 kcal surplus does.
How to tell whether it is working
Three signals, read together over weeks rather than days. The first is the weight trend: weigh yourself under the same conditions most mornings and compare the average of one week against the average of the week before. Single readings swing a kilogram on gut contents and fluid alone, which is more than a fortnight of real gain. The second is the waist: measured at the navel at the end of a normal breath out, monthly, in the same conditions. A waist that is climbing faster than the weight is telling you the surplus is outrunning what your training can use.
The third is strength, and it is the one that separates a working plan from an expensive one. If the weight is going up, the waist is roughly holding, and the lifts are moving, the plan is doing its job. If the weight is going up, the waist is going up faster, and the lifts are flat, the surplus is too large or the programme is not progressing, and eating more will fix neither.
Re-run this calculator with your current weight every four to six weeks. Maintenance calories rise as you get heavier, so the target that produced 0.35 kg a week at the start will produce less than that three months in. The correct target grows with you.
When to stop, and what to do next
Most people should stop a gaining phase when one of three things happens: the goal weight is reached, body fat has climbed further than they want to diet back off, or the weight is still rising while strength has been flat for a couple of months. The last case is the clearest: the surplus has stopped being converted into anything useful.
From there the choice is maintenance or a deficit. Moving to maintenance means dropping intake back to your estimated TDEE and holding the new weight for a few weeks, which is worth doing before any cut simply so you know where maintenance actually sits at the heavier bodyweight. If the aim is to shed the fat added during the gaining phase, the calorie deficit calculator applies the mirror-image rails to the way down, and the same protein range applies, arguably more strictly, because a deficit is where lean mass is genuinely at risk.
Cycling between modest gaining phases and modest cuts over years is unremarkable and effective. Alternating between extreme ones mostly produces a lot of weight moving in both directions and not much lasting change in composition.
Who should not run a gaining phase
Anyone under 18: the adult equations here are not valid for growing bodies, and this calculator will not produce a number for minors. Anyone who is not doing resistance training, because without the stimulus the surplus has nowhere useful to go. Anyone already above a BMI of 27.5 for their height, which is the ceiling written into the calculation: adding weight from there is not a lean gain in any meaningful sense, whatever the plan is called.
It is also the wrong tool if the goal is to gain weight for a clinical reason: recovery from illness, an eating disorder, unintentional weight loss, or a medically supervised increase in intake. Those need a dietitian who can see the whole picture, not a web form with a BMI ceiling. And if the number on the scale, rather than what you can lift, has become the thing you think about most, that is worth raising with a GP before adding a target to it.
How it's calculated
Maintenance calories (Mifflin–St Jeor BMR × activity factor)
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 (men) or − 161 (women) · TDEE = BMR × activity factor (1.2 sedentary to 1.9 extra active)
The activity multipliers are population estimates; the TDEE they produce carries roughly a ±10–15% error band for an individual.
Daily surplus from a weekly rate
Daily surplus (kcal) = weekly rate (kg) × 7,700 ÷ 7 · Daily target = TDEE + daily surplus
7,700 kcal per kilogram is Wishnofsky's energy equivalent of body tissue. It was derived for weight loss and assumes ordinary bodyweight rather than pure muscle, so it is a planning approximation, not a conversion rate.
The caps applied to that target
Weekly rate ≤ 0.005 × weight(kg) · Daily target ≤ TDEE × 1.20 · Goal weight ≤ 27.5 × height(m)²
Whichever binds first wins, and the result panel says which one was applied and why.
Protein target
Protein (g/day) = 1.6 to 2.2 × weight(kg)
The interval from Morton et al.'s meta-analysis, where lean-mass gains plateaued at about 1.6 g/kg with the confidence interval extending to 2.2.
Weeks to a goal weight
Weeks = (goal weight − current weight) ÷ planned weekly rate
Shown only when a goal weight is entered, and rounded to whole weeks. The planned rate will not hold exactly, because maintenance calories rise as you get heavier.
Worked example: a 30-year-old man, 180 cm and 80 kg, training three to five days a week
- BMR by Mifflin–St Jeor: 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal.
- Maintenance: 1,780 × 1.55 (moderately active) = 2,759 kcal a day.
- Chosen rate, the standard 0.35 kg a week. Check the cap first: 0.005 × 80 = 0.4 kg a week, so 0.35 is inside it and passes through unchanged.
- Daily surplus: 0.35 × 7,700 ÷ 7 = 2,695 ÷ 7 = 385 kcal.
- Daily target: 2,759 + 385 = 3,144 kcal. The page displays it rounded to the nearest ten, as 3,140 kcal.
- Check the surplus cap: 20% of 2,759 is 552 kcal, and 385 is below it, so no second cap applies. The surplus is 385 ÷ 2,759 = 14% above maintenance.
- Protein: 80 × 1.6 = 128 g to 80 × 2.2 = 176 g a day.
- With a goal weight of 86 kg entered: (86 − 80) ÷ 0.35 = 17.1, so about 17 weeks, and the BMI 27.5 ceiling for 180 cm is 27.5 × 1.8² = 89.1 kg, so the goal is inside it.
- Reading it against training age: at 0.35 kg a week this man gains about 1.5 kg a month. If he is in his first year of training, perhaps 0.8–1.2 kg of that could be muscle. If he is in his fifth, more like 0.2–0.4 kg, and the conservative 0.2 kg a week setting would be the better choice.
Where this number is used in the real world
- Strength and physique training, where a gaining phase is planned deliberately between competition or testing blocks rather than drifted into.
- Sport with weight classes or positional mass requirements (rowing, rugby, throwing events), where adding mass is part of the programme and the composition of it is scrutinised.
- Clinical and dietetic practice as a starting estimate for supported weight gain, before individual assessment adjusts it.
- Recovery of weight lost to illness, injury or a long training layoff, where regaining previously held muscle happens faster than building it originally.
- Adolescent-to-adult athletes finishing growth and moving to an adult programme, where the adult equations become valid and the rate guidance changes.
- Anyone who has spent years unintentionally eating at maintenance and cannot understand why the training is not showing: the arithmetic here usually explains it in one line.
- Planning the mirror image of a diet: knowing what maintenance and a modest surplus look like makes the deficit you will run afterwards much easier to size.
Frequently asked questions
How many calories above maintenance should I eat to build muscle?
For most people, between 10% and 20% above maintenance, commonly 200 to 500 kcal a day. Newer lifters can use the upper end because they can convert more of it into muscle; experienced lifters should sit at the lower end, since their ceiling on muscle gain is lower and the surplus above that ceiling becomes fat. This calculator sizes the surplus from the weekly rate you pick and then holds it at 20% of your maintenance calories if the arithmetic would have gone higher, because past that point the extra food buys nothing the training can use.
Why does this calculator refuse to plan a faster bulk?
Because gaining faster than about 0.5% of bodyweight a week does not add muscle faster; it adds fat faster. Muscle protein synthesis is limited by the training stimulus and recovery, not by how much food is available once the basic requirement is met, so calories beyond that ceiling have one destination. The controlled-surplus research in athletes shows both groups gaining lean mass at a similar rate while the faster group gains substantially more fat. A cap is the honest response to that, and there is no setting on this page that switches it off.
How much muscle can I actually gain in a month?
It depends almost entirely on training age. Commonly used practical guidance puts the first year of consistent resistance training at roughly 1–1.5% of bodyweight a month, the second year at around 0.5–1%, and the third year and beyond at 0.25–0.5% or less. Those ranges are coaching rules of thumb rather than published regressions, and individual variation is wide. Use them as a ceiling on what a surplus can be converted into: if the scale is moving much faster than your training age allows, the surplus is larger than it needs to be.
Can I build muscle without a calorie surplus?
Sometimes, yes. People new to resistance training, people returning after a break, and people carrying a substantial amount of body fat can add muscle while eating at or below maintenance, because stored fat supplies the energy for it. The review by Slater and colleagues sets this out clearly: a surplus supports hypertrophy rather than being mechanically required for it. For a lean, experienced lifter the picture is different: at that end, adding muscle without at least a small surplus is slow going, and a modest surplus is the practical route.
How much of the weight I gain will be fat?
There is no fixed ratio, which is why nobody honest quotes one. The share of the gain that is lean tissue rises with training quality, adequate protein and a slower rate, and falls with training age, a larger surplus and inadequate protein. A first-year lifter eating a modest surplus with 1.6–2.2 g/kg of protein and a progressing programme can see most of the gain as lean tissue. A ten-year lifter running a large surplus can see almost none of it, because the muscle ceiling has already been reached and everything above it is stored.
Why did the calculator reject my goal weight?
Two reasons trigger it. If your goal weight is at or below your current weight, this is the wrong tool and the calorie deficit calculator is the right one. If the goal sits above a BMI of 27.5 for your height, the plan is refused because at that point calling the extra kilograms a lean gain is no longer accurate. The calculator shows the ceiling weight for your height so you can set a goal under it. You can reach the ceiling, hold it, reassess and set a new goal from there; what you cannot do is have the page plan straight through it.
Do I need to eat more protein during a gaining phase than during a cut?
Not really: the same 1.6–2.2 g per kilogram range applies in both. During a deficit the priority is holding onto existing lean mass; during a surplus it is supplying material for new tissue. The evidence puts the useful intake for both at a similar place, and Morton's meta-analysis found gains stopped improving above about 1.6 g/kg with resistance training. What does change is the rest of the plate: in a surplus there is far more room for carbohydrate, which is what fuels the training that makes the surplus worth running.
How long should a gaining phase last?
Long enough for the training to show something, which usually means months rather than weeks. Twelve to twenty is a common block. Stop when the goal weight is reached, when body fat has risen further than you want to diet back off, or when the weight is still climbing while strength has been flat for two months, which means the surplus has stopped being converted into anything useful. Move to maintenance for a few weeks before deciding what comes next, if only to find out where maintenance now sits at the heavier bodyweight.
Keep going
A single number rarely tells the whole story. Alongside the calorie surplus result, the TDEE calculator, the macros calculator, the protein calculator, the calorie deficit calculator and the FFMI calculator each add a different angle on the same measurements. For the reasoning behind the numbers, read TDEE explained and Track without DEXA.
Sources
- Garthe I, Raastad T, Refsnes PE, Sundgot-Borgen J. Effect of nutritional intervention on body composition and performance in elite athletes. Eur J Sport Sci 2013;13:295–303. doi.org/10.1080/17461391.2011.643923
- Slater GJ, Dieter BP, Marsh DJ, Helms ER, Shaw G, Iraki J. Is an energy surplus required to maximize skeletal muscle hypertrophy associated with resistance training? Front Nutr 2019;6:131. doi.org/10.3389/fnut.2019.00131
- Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med 2018;52:376–84. doi.org/10.1136/bjsports-2017-097608
- Iraki J, Fitschen P, Espinar S, Helms E. Nutrition recommendations for bodybuilders in the off-season: a narrative review. Sports 2019;7:154. doi.org/10.3390/sports7070154
- Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr 1958;6:542–6. doi.org/10.1093/ajcn/6.5.542
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- “Calorie Surplus Calculator”, Body Stats, last updated 12 September 2026, https://bodystats.co/app/calorie-surplus-calculator
Every formula and threshold on this page is written out with its primary source on our methodology page. These results are informational and educational, not a diagnosis or a substitute for professional advice. See the medical disclaimer.
Last updated . Written by Rick Campbell; not medically reviewed. See review status.