How Big a Calorie Surplus You Actually Need to Build Muscle

You want to put on muscle, so you know you need to eat more. One person tells you to add 200 calories a day, another says 500, and somebody at the gym says to eat everything that isn't nailed down. How big does the surplus actually need to be?

Smaller than the gym advice suggests. A sensible range is about 5 to 15 percent above maintenance, adjusted until your weight climbs by roughly a quarter to a half percent of your bodyweight per week. Go much past that and the extra food seems to land mostly as fat.

Nobody has found the exact number

It helps to know up front that this is an estimate. The most useful review on the question, by Slater and colleagues, says plainly that the specific surplus needed to support muscle growth is unknown. Textbook figures are often worked out from the energy stored in the tissue itself, and that calculation leaves out a lot.

The stored energy is smaller than you might guess. The review puts it at about 5,000 to 5,200 kilojoules per kilogram of muscle, which is roughly 550 calories per pound. Building that tissue costs more than what ends up stored in it, and one estimate the authors cite comes to about 800 calories per pound. The authors also note that no study has shown a consistent energy cost for muscle gained through lifting, so treat those as rough figures.

Either way, the arithmetic points in the same direction. Even a good rate of muscle gain does not call for a huge daily surplus. The review's practical advice is to start conservatively, at around 1,500 to 2,000 kilojoules a day (about 360 to 480 calories), then adjust based on how your body responds.

What happens when the surplus gets bigger

Two trials compared different amounts of food directly, and they are worth reading together.

Helms and colleagues randomized trained lifters to eat at maintenance, 5 percent above it, or 15 percent above it for eight weeks while lifting three days a week. The evidence favored more skinfold gain in the 15 percent group than at maintenance, and the authors' overall read was that faster weight gain primarily increased the rate of fat gain, not muscle size or strength.

That trial has limits, and the result was not one-sided. COVID-19 cut the sample to 17 people who finished, so the numbers are small. The 15 percent group did gain more on the bench press, and biceps thickness may have benefited slightly from faster weight gain. For squat strength and muscle thickness, there was no evidence of a difference between groups.

Garthe and colleagues ran a similar comparison in 39 young elite athletes over 8 to 12 weeks, all doing four added strength sessions a week. One group followed a meal plan built for weight gain and ate about 3,585 calories a day. The other ate as they pleased and averaged about 2,964. The meal-plan group gained more bodyweight, 3.9 percent against 1.5 percent, and their fat mass rose by 15 percent against 3 percent. Lean mass gain did not differ between the groups.

Neither study settles it for every lifter over every timescale. Both ran for only a few months, and elite athletes are not typical gym-goers. But they lean the same way: past a modest surplus, you pay more in body fat than you get back in muscle.

Turning that into your number

Start from your actual maintenance calories, not a guess. If you have been eating steadily and your weight has held, that intake is your baseline. A percentage of a wrong number is still wrong.

Say you weigh 170 pounds and maintain on 2,700 calories. Using the rough rule of 3,500 calories per pound of weight change, here is how the options look on paper:

• 5 percent: 135 extra calories, 2,835 total, about 0.3 pounds a week.
• 10 percent: 270 extra calories, 2,970 total, about 0.5 pounds a week.
• 15 percent: 405 extra calories, 3,105 total, about 0.8 pounds a week.

Compare those with the target in a review of off-season bodybuilding nutrition by Iraki and colleagues: about 0.25 to 0.5 percent of bodyweight per week for novice and intermediate lifters. At 170 pounds, that is about 0.4 to 0.85 pounds a week, which sits right in the band above. The macro calculator uses the same three steps for its build rates, and it is a starting point to adjust from rather than a prescription.

How much depends on how long you have been lifting

Training experience shifts the answer. The Iraki review suggests 10 to 20 percent above maintenance for novice and intermediate bodybuilders, and 5 to 10 percent with slower weight gain, around 0.25 percent a week, for advanced ones. The logic is that newer lifters have more muscle available to gain, so they can put a larger surplus to use. Given the two trials above, starting in the lower half of your range is the safer bet, since it is easy to add food later.

• Newer to lifting: try about 10 percent.
• A few years in: try 5 to 10 percent.
• Years of serious training and still progressing: stay near 5 percent, and expect slow progress.

Those bands are a judgment call drawn from the review and the two trials, not a tested protocol. And you may not need a surplus at all. If you are new to lifting and carrying some extra fat, the Slater review notes that muscle growth is possible even in a deficit for people in that position, so recomposition at maintenance may be the better first move.

Where the extra calories should come from

Less hangs on this than people expect. Protein does not have to climb with your calories. The meta-analysis by Morton and colleagues found that lean mass gains stopped improving at about 1.62 grams per kilogram a day, or roughly 0.74 grams per pound. If you already hit your protein target, the surplus does not need to go there.

Slater and colleagues concluded that once minimum macro targets are met, the source of the surplus does not appear to bring any metabolic or functional benefit. So keep your fat above a sensible floor and put the extra wherever it is easiest to eat and train on. For most people who lift hard, that means more carbs, usually around training.

Let the scale correct the plan

The percentage only gets you started. Your own rate of gain is what tells you whether it is right, since your real maintenance and how much your daily movement shifts when you eat more are both unknowns.

Weigh yourself most mornings and compare weekly averages, not single days. Ignore the first week or so, when more food in your gut and more water can move the scale on their own. Then check two or three weeks of trend against your target rate.

If the average is not moving, add 100 to 150 calories a day and give it another two weeks. If it is climbing faster than about 0.5 percent a week, take the same amount back out. That step size is a coaching habit, not a research finding, but small changes are easier to read through the noise.

The short version

Nobody has pinned down the ideal surplus, but the trials so far suggest that eating well past a modest one mostly buys you fat. Start 5 to 15 percent above real maintenance, toward the low end if you have been lifting for years. Aim to gain about 0.25 to 0.5 percent of your bodyweight a week, and let your weekly averages decide when to change the number.

If you don't have a baseline yet, run your stats through the calculator and eat at that number for a couple of weeks before you add anything. The training is what asks for the muscle. The surplus only has to keep up.