How Many Calories to Build Muscle? The Surplus You Need, by Training Age

You've decided to build muscle, so you look up how much to eat. One source says to add 500 calories. A forum says to eat 4,000 a day and never miss a meal. A calculator gives you a number down to the single calorie, as if it knows how much you fidget at your desk.

So you guess. Eight weeks later, either the scale hasn't moved and your arms look the same, or it's moved a lot and most of it has landed on your waist. Both outcomes feel like you did something wrong. Usually you just never had a number that fit you.

The fix is a small, measured surplus that you check against the scale and adjust. Below you'll find the numbers at a glance, how to find your maintenance calories, how big a surplus to add for your training age, what a pound of muscle actually costs, protein, the rate of gain to aim for and how to adjust after 2 to 4 weeks. You'll also get an honest answer to how to bulk up fast, and what 1,200, 2,500 and 3,000 calories a day mean for building muscle.

How Many Calories to Build Muscle: The Numbers at a Glance

Your surplus is a percentage of your maintenance calories, and the right percentage shrinks the longer you've been lifting. Here's what that means in calories at three common maintenance levels.

The ranges come from Iraki and colleagues (2019), who reviewed off-season nutrition for natural bodybuilders. They recommended a surplus of about 10 to 20 percent and a weekly gain of 0.25 to 0.5 percent of body weight for novice and intermediate lifters, and a more conservative approach for advanced ones. The split into three rows, and the trimmed top end, is my coaching judgment built on their range, because a later trial found that bigger surpluses mostly added fat. Treat each row as a starting point that you'll adjust after a few weeks.

Step 1: Find Your Maintenance Calories

Maintenance is the number of calories that keeps your weight steady, also called your total daily energy expenditure. Every surplus is built on top of it, so an error here becomes an error in everything else. You'll estimate it first and then check it.

Estimate It With an Equation

The Mifflin-St Jeor equation was built from measurements of resting energy use in 498 healthy adults (Mifflin and colleagues, 1990). It estimates the calories you burn at rest:

• Men: 10 × weight in kg, plus 6.25 × height in cm, minus 5 × age, plus 5
• Women: 10 × weight in kg, plus 6.25 × height in cm, minus 5 × age, minus 161

Multiply the result by an activity factor: 1.2 if you're sedentary, 1.375 for 1 to 3 workouts a week, 1.55 for 3 to 5 and 1.725 for 6 or 7. Our TDEE calculator does the math for you with the same equation and factors. Two worked examples:

• A 30-year-old man who weighs 75 kg (165 lb), stands 178 cm (5 ft 10 in) and lifts 3 or 4 times a week burns about 1,720 calories at rest and about 2,660 a day in total.
• A 28-year-old woman who weighs 62 kg (137 lb), stands 165 cm (5 ft 5 in) and trains just as often burns about 1,350 at rest and about 2,090 a day in total.

That's a good first guess, and only a guess. In a systematic review of the common equations, Frankenfield and colleagues (2005) found Mifflin-St Jeor was the most reliable, predicting resting needs within 10 percent of the measured value in more people than any other equation. For the 75 kg man, a 10 percent miss on his resting estimate carries through the activity factor to about 265 calories a day, which is as big as the whole surplus a beginner needs. The activity factor adds its own error on top. So the estimate gets you close, and your scale finishes the job.

Confirm It With Two Weeks of Weigh-Ins

Eat at your estimate as consistently as you can for two weeks. Weigh yourself each morning after using the bathroom and before eating, and average each week's readings. If the two weekly averages are within about 0.2 kg (half a pound) of each other, you've found maintenance. If your weight is climbing, your real maintenance is lower than the estimate; if it's falling, it's higher. Move your number 100 to 200 calories in the right direction and check again.

Step 2: Pick a Surplus That Matches Your Training Age

Beginners can build muscle fastest, so they can put more extra food to good use. In their review of whether a surplus is needed at all, Slater and colleagues (2019) concluded that the ideal surplus has never been tested in people who lift. They suggested starting at about 1,500 to 2,000 kilojoules a day, roughly 360 to 480 calories, and watching how your body responds. That's close to the beginner row of the table.

Experienced lifters add muscle slowly. The same 400 extra calories that fed real growth in your first year mostly turns into fat by your fifth, which is why the surplus shrinks as your training age grows. If you've had months off, use the beginner row, because regaining muscle you've built before tends to go faster than building it the first time.

If you want the smallest possible fat gain, stay at the bottom of your row. That's a lean bulk: a surplus of about 5 to 10 percent held for several months, with mostly whole foods doing the work. Our guide to what a lean bulk is covers its macros, a sample day of eating and when to end one.

How Many Calories Does It Take to Build a Pound of Muscle?

Fewer than many websites say. Figures of 2,500 calories or more per pound of lean mass circulate widely, but the research estimates are much lower. Slater's review notes that the energy stored in a kilogram of muscle is about 5,000 to 5,200 kilojoules, roughly 1,200 calories, because muscle is mostly water. The estimates it cites for the full cost of building that kilogram, including the work of making new protein, run from about 6,050 to 7,440 kilojoules, or roughly 1,450 to 1,780 calories. Per pound, that's about 650 to 800 calories.

So a beginner who adds a full kilogram (2.2 pounds) of muscle in a month, which is a fast rate, needs only about 50 to 60 extra calories a day for the tissue itself. The rest of a 250- to 500-calorie surplus covers the error in your maintenance estimate, the extra energy your body burns when you eat more and the training itself. Whatever is left over gets stored, mostly as fat. That's why the surplus should stay modest: the muscle itself costs little, and every calorie beyond what you can use is stored.

Step 3: Set Your Protein, Then Fill In Carbs and Fat

Calories decide whether you gain weight. Protein and training decide how much of that weight is muscle. Morton and colleagues (2018) pooled 49 trials with 1,863 participants and found that extra protein boosted gains in fat-free mass during resistance training up to a total intake of about 1.62 g per kg of body weight a day. Above that, it added nothing more on average.

Iraki's review turns that into a daily plan for building muscle:

• Protein: 1.6 to 2.2 g per kg a day, spread over 3 to 6 meals of about 0.4 to 0.55 g per kg each.
• Fat: 0.5 to 1.5 g per kg a day.
• Carbohydrate: the rest of your calories, and at least 3 to 5 g per kg a day to fuel training.

Here's the 75 kg man from Step 1 as a beginner eating about 2,950 calories a day, a surplus of about 290 calories or 11 percent. Protein at 1.8 g/kg is 135 g (540 calories). Fat at 1 g/kg is 75 g (675 calories). The remaining 1,735 calories come from about 435 g of carbohydrate, or roughly 5.8 g/kg. A day built around eggs, yogurt, chicken or tofu, rice, potatoes, oats, fruit and a handful of nuts gets there without anything unusual.

How Fast Should You Gain Weight When Building Muscle?

For novice and intermediate lifters, Iraki's review suggests gaining 0.25 to 0.5 percent of body weight a week. Here's what that looks like on the scale:

Not all of that is muscle. Some fat and water come along with it, even when the surplus is small. Beginners can work toward the top of each range, intermediates toward the bottom and advanced lifters below it.

Expect a jump in the first week that has nothing to do with muscle or fat. Your body stores carbohydrate as glycogen, and Kreitzman and colleagues (1992) describe glycogen as stored with three to four parts water. Eat more carbohydrate and you hold more glycogen, more water and more food in your gut, so ignore week one when you judge your rate. If keeping fat gain small is your main concern, our guide to gaining muscle without gaining fat adds waist and strength checks to these targets.

Step 4: Adjust Your Calories After 2 to 4 Weeks

Your starting number will be off by some amount, and the scale will tell you which way. Use these rules:

• Compare weekly averages, not single days. Daily weight swings with salt, water, carbs and digestion. Weigh most mornings and average each week.
• Give each number at least two weeks, not counting the first week of a new surplus.
• Gaining slower than your target? Add 100 to 150 calories a day.
• Gaining faster than your target? Take away 100 to 150 calories a day.
• Check your training too. Your reps or weights should climb over the weeks. If your waist is growing quickly while your lifts stay flat, the surplus is too big for what your training can use.
• Change one thing at a time, then wait another two weeks.

If you've been eating what feels like a lot and the scale won't move, your body may be burning part of the extra. Levine, Eberhardt and Jensen (1999) overfed 16 non-obese adults by 1,000 calories a day for eight weeks. Two-thirds of the rise in their daily energy use came from non-exercise activity such as fidgeting, posture and moving around, and those differences explained a tenfold range in how much fat people stored. Some people really do need more food than a calculator says. The fix is the same small steps: add 150 calories, wait two weeks and repeat. When appetite is the limit, lean on calorie-dense foods such as milk, nuts, nut butter, olive oil, dried fruit and smoothies.

How to Bulk Up Fast (and Why Faster Mostly Adds Fat)

The realistic fast rate is about 0.5 percent of body weight a week, which is 0.35 to 0.45 kg (0.8 to 1 lb) for a beginner who weighs 70 to 90 kg. Past that, most of the extra weight is fat, because muscle grows at the pace your training sets, not the pace your appetite sets.

Two trials show what happens when you push harder. Garthe and colleagues (2013) randomized 39 elite athletes to a meal plan built to gain weight or to eating freely for 8 to 12 weeks, while all of them added four strength sessions a week. The meal-plan group ate 3,585 calories a day against 2,964 and gained more weight (3.9 percent against 1.5 percent). Their fat mass rose 15 percent against 3 percent, and lean mass gains didn't differ between the groups.

Helms and colleagues (2023) then randomized 21 trained lifters to maintenance, a 5 percent surplus or a 15 percent surplus for eight weeks, and 17 finished. Faster weight gain predicted bigger increases in skinfold thickness, explaining about half of the variation, but did little for muscle thickness or squat strength. Bench press strength did rise more in the 15 percent group. The authors concluded that faster gain mainly adds fat.

What actually speeds up muscle gain is training and consistency, not food. Train each muscle with hard sets that end a few reps short of failure at least twice a week, add reps or weight as you get stronger, hit your protein, sleep at least seven hours and don't skip weeks. You can do all of that at home with dumbbells and your body weight. Our roundup of the best dumbbell workout apps compares the options for training that way. FitCraft is one of them: a 3D AI coach demonstrates every exercise on an interactive 3D model and says your name during the workout, your workouts adapt as you progress, and streaks reward the weeks you don't skip.

Before you speed anything up, check whether a bulk is the right phase for you at all. If you're carrying a fair amount of body fat, more of a surplus goes to fat, and cutting first or holding at maintenance often works better. Our guide to bulking vs cutting explains where those cutoffs sit and which phase to run first.

Is 2,500 or 3,000 Calories Enough to Build Muscle?

It depends entirely on your maintenance, because the same number can be a surplus for one person and a deficit for another. Using the Mifflin-St Jeor examples from Step 1:

• The 75 kg man (maintenance about 2,660): 3,000 calories is a surplus of about 340, or 13 percent, which suits a beginner. 2,500 is about 160 below maintenance, so muscle gain would be slow at best.
• The 62 kg woman (maintenance about 2,090): 2,500 calories is a surplus of about 410, or almost 20 percent, which is more than she needs. About 2,300 to 2,400 would do.
• A 25-year-old man who weighs 90 kg (198 lb), stands 185 cm (6 ft 1 in) and trains 6 days a week (maintenance about 3,340): 3,000 calories is a deficit of about 340. He'd need roughly 3,500 to 3,700 to be in a surplus.

So don't pick a round number. Use your maintenance plus the surplus from your row of the table.

Can You Build Muscle on 1,200 Calories or in a Calorie Deficit?

1,200 calories is below even the resting needs of the 62 kg woman in Step 1, about 1,350, so it's a deficit for almost every adult. Building muscle on it is unlikely, and eating that little shouldn't be a plan without medical supervision.

Deficits in general work against muscle gain. Murphy and Koehler (2022) pooled trials of resistance training in an energy deficit lasting at least three weeks. Lean mass gains were impaired compared with training without a deficit, while strength gains held up. Their meta-regression found that a deficit of about 500 calories a day was enough to prevent lean mass gains.

A 1,000-calorie deficit can still allow some muscle gain in one unusual setting. Longland and colleagues (2016) gave 40 young men a diet about 40 percent below their needs for four weeks, plus hard resistance and interval training 6 days a week. The group eating 2.4 g of protein per kg a day gained 1.2 kg of lean mass and lost 4.8 kg of fat. The group eating 1.2 g/kg gained 0.1 kg of lean mass. That's a short, tightly controlled study with all food provided. It shows what's possible for four weeks, and it isn't a sensible everyday plan.

If losing fat is your main goal, keep any deficit to about 500 calories a day or less, keep protein high and keep training hard. You'll hold on to most of your muscle, and beginners often add some.

How Many Calories Should a Woman Eat to Gain Muscle?

Women build muscle at the same relative rate as men on the same program. Roberts, Nuckols and Krieger (2020) pooled studies that put men and women through identical resistance training and found no significant difference in relative muscle growth. So the same percentages apply, and the calories are usually smaller only because maintenance is usually lower.

For the 62 kg woman with a maintenance of about 2,090, a beginner surplus of 10 to 15 percent is about 210 to 315 calories, or roughly 2,300 to 2,400 a day. Her weekly gain target is 0.15 to 0.3 kg (0.3 to 0.7 lb). Body weight can swing with water across the menstrual cycle, so compare averages from the same point in your cycle, or average over a full month, before changing your number.

The Bottom Line

How many calories to build muscle comes down to two numbers: your maintenance and a modest surplus on top of it. Estimate maintenance with an equation, confirm it with two weeks of weigh-ins, add about 10 to 15 percent as a beginner and less as you gain experience, and set protein at 1.6 to 2.2 g per kg. Aim for 0.25 to 0.5 percent of body weight a week, and adjust by 100 to 150 calories every few weeks based on your averages.

The food is the easy part to get right. Showing up to train week after week is what turns a surplus into muscle. As one FitCraft user, Mike, said after four months of getting visibly stronger: "The streak system got me hooked. I didn't want to break my chain."