How many calories you need to build muscle

Why a surplus

Building new muscle is work, and your body needs energy and material for it. When you eat exactly what you burn, muscle can grow, but slowly. When you eat less, your body saves energy, and growth almost stops.

There are exceptions: a beginner, someone coming back after a long break, or someone with plenty of fat to spare can build muscle at maintenance or even in a small deficit. But if you've been training for a couple of years and want to grow, you need a surplus — a small, controlled one.

How much more to eat

I go with 5–15% over maintenance: for someone with a maintenance of 2,700 kcal, that's about 2,850–3,100 kcal a day. It's easier to measure the rate of gain than the calories: the review by Iraki et al. (2019) recommends gaining about 0.25–0.5% of bodyweight a week. For 80 kg that's 0.2–0.4 kg a week, or about 1–1.5 kg a month.

A beginner can go closer to the top end: they grow faster, and the extra energy gets used. Someone who has trained for several years should go closer to the bottom: their muscle grows more slowly, and a big surplus turns into fat.

How to find your maintenance

Start with a formula: the calorie calculator works out your resting energy with Mifflin–St Jeor, multiplies it by your activity and gives you a bulking range right away. It's an estimate: two people with the same height and weight can burn hundreds of calories apart.

So the formula is a starting point, not the answer. Eat roughly the same for two weeks and weigh yourself. If your weight holds steady, that's your maintenance. If it drifts down, you were eating less than you thought. Add the surplus on top of that.

Weigh yourself the right way

Bodyweight swings by 1–2 kg in a day: water, salt, food in your stomach, yesterday's leg day. A single weigh-in tells you nothing. Here's what works:

• Weigh yourself under the same conditions — in the morning, after the bathroom, before eating.
• At least once a week, better 3–4 times.
• Compare weekly averages, not single days.

There's a weight diary in the bot and in the app: log your weight and I'll show you the trend.

How to adjust

Look at the trend over 2–3 weeks:

• Weight not moving — add 100–200 kcal a day: a slice of bread with peanut butter, a glass of milk, an extra handful of rice.
• Going up by 0.25–0.5% a week — leave it alone.
• Going up faster — take away 100–200 kcal. The extra goes to fat, not muscle.

Change things a little at a time and wait two weeks: your body doesn't respond in three days. Big swings in your eating muddy the picture, and you can't tell what worked.

Without training, a surplus is just fat

The surplus provides material; training provides the signal to grow. You need enough hard sets per muscle per week — in the meta-analysis by Schoenfeld, Ogborn and Krieger (2017), growth followed volume — and a load that rises over time. How to put that together is in the guide on a muscle gain program.

And protein: about 1.6 g per kg of bodyweight a day (the Morton et al. 2018 meta-analysis). Calories without protein mostly build fat.

The dirty bulk

"Eat everything you see" is old advice with a high price. A big surplus doesn't speed up muscle growth: growth has a limit, and everything above it goes to fat. Then you'll have to cut that fat, and a cut is months in a deficit, during which you grow more slowly.

If your bodyweight goes up by more than a kilo a week for longer than a couple of weeks, that's not muscle anymore. Cut back the extra, and in six months you'll have more muscle and less fat than after a "bulk at any cost". How to lose the fat later without losing your progress is in the guide on cutting without losing muscle.

Common questions

I can't eat that much. Drink your calories: milk, a shake with oats, banana and peanut butter. Add one more meal rather than eating huge portions.

How long should a bulk last? As long as your lifts are going up, your bodyweight is in range and your fat isn't visibly piling on. Usually that's months, not weeks.

Do I have to count calories? No. You can eat as usual and adjust by the scale — that's even more honest than trusting labels. I don't count food, but I'll show your weight trend and strength gains.

Read next

• Calories per day
• Protein per day
• A workout program for muscle gain
• How to cut without losing muscle