To gain muscle, you need to eat roughly 5 to 20% more calories than your body burns each day. For someone whose maintenance level is 2,000 calories, that means eating 2,100 to 2,400 calories daily. The exact number depends on your size, activity level, and how aggressively you want to gain, but that modest surplus gives your body the energy it needs to build new tissue without piling on unnecessary fat.
Finding Your Maintenance Calories
Before you can calculate a surplus, you need a baseline: the number of calories your body burns in a normal day just to keep you alive and moving. This is your total daily energy expenditure, or TDEE. The most widely used method starts with the Mifflin-St Jeor equation, which estimates your resting calorie burn based on your size and age.
For men, the formula is: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5. For women, it’s the same but you subtract 161 instead of adding 5. So a 30-year-old man who weighs 80 kg (176 lbs) and stands 180 cm (5’11”) would get a resting number of about 1,780 calories.
That resting number only covers what your body burns at complete rest. You then multiply it by an activity factor to account for daily movement and exercise:
- Sedentary (desk job, little exercise): multiply by 1.2
- Lightly active (light exercise 1–3 days/week): multiply by 1.375
- Moderately active (moderate exercise 3–5 days/week): multiply by 1.55
- Very active (hard exercise 6–7 days/week): multiply by 1.725
Using the example above, that 30-year-old man lifting weights four days a week would multiply 1,780 by 1.55, landing at roughly 2,760 maintenance calories. That’s his starting point.
How Much to Add Above Maintenance
A surplus of 5 to 20% above maintenance is the range most consistently supported for building muscle while keeping fat gain in check. At the low end (5%), you’re adding just 100 to 150 extra calories, which works well if you’re already fairly lean and want to stay that way. At the higher end (20%), you’re adding 400 to 550 calories, which can accelerate muscle gain but will also bring more fat along for the ride.
Starting at the lower end is the smarter move. A conservative surplus gives your body enough raw material to build muscle without a large excess that simply gets stored as fat. You can always increase later if the scale isn’t moving. For our 2,760-calorie example, a 10% surplus would mean eating about 3,035 calories daily.
A useful way to gauge whether your surplus is dialed in: aim for a weight gain of about 0.25 to 0.5% of your body weight per week. For a 180-pound person, that’s roughly 0.5 to 0.9 pounds per week. Gaining faster than that usually signals you’re adding more fat than muscle. Gaining slower may mean you need a few more calories or that your training needs to catch up.
Protein, Carbs, and Fat Ratios
Total calories matter most, but how you split those calories between protein, carbohydrates, and fat influences whether that surplus turns into muscle or just body fat. A well-supported ratio for muscle gain is 45 to 50% of calories from carbohydrates, 30 to 35% from protein, and 20 to 25% from fat.
On a 2,500-calorie diet, that breakdown looks like roughly 280 to 310 grams of carbs, 185 to 220 grams of protein, and 55 to 70 grams of fat. Carbs fuel your workouts and help replenish the energy stores in your muscles afterward. Fat supports hormone production, including testosterone, which plays a direct role in muscle growth. Protein provides the building blocks your muscles are actually made of.
For protein specifically, people who lift weights regularly benefit from 1.2 to 1.7 grams per kilogram of body weight each day. For a 180-pound (82 kg) person, that’s about 98 to 139 grams. Going above 2 grams per kilogram (around 164 grams for that same person) is generally considered excessive and doesn’t appear to produce additional muscle-building benefits.
Training Has to Match the Surplus
Extra calories without a strong training stimulus won’t build muscle. They’ll just build fat. Your body needs a clear signal that muscle is in demand, and that signal comes from resistance training with enough volume and intensity to challenge your muscles beyond what they’re used to.
Research from the University of New Mexico compared low-volume (1 set per exercise), moderate-volume (3 sets), and high-volume (5 sets) programs in trained men. All three produced some muscle growth, but higher volume produced the greatest gains. The researchers recommended 4 to 6 sets per exercise as a practical ceiling, noting that going beyond that range may lead to overtraining and diminishing returns.
Training three to five days per week with compound exercises (movements that work multiple joints, like squats, presses, rows, and deadlifts) is the most efficient way to ensure your surplus gets directed toward muscle. If you’re eating in a surplus but only training once or twice a week with light weights, the math doesn’t work in your favor.
Adjusting Over Time
Your calorie needs aren’t fixed. As you gain muscle, your body burns more calories at rest, which means your maintenance level creeps upward. A surplus that worked at 175 pounds may become a maintenance intake at 185 pounds. Recalculating every four to six weeks keeps you on track.
Weigh yourself at the same time each day, ideally in the morning before eating, and use a weekly average rather than any single reading. Daily fluctuations from water, food volume, and salt intake can swing your weight by two or more pounds in either direction, which makes individual weigh-ins misleading. If your weekly average is climbing at that 0.25 to 0.5% rate, your surplus is working. If it’s climbing faster, pull back by 100 to 200 calories. If it’s flat for two consecutive weeks, add 100 to 200 calories.
Body measurements can be even more useful than the scale. Tracking the circumference of your arms, chest, and thighs alongside your waist gives you a clearer picture of where new tissue is going. A growing chest with a stable waist is a good sign. A growing waist with stable arms means you’re likely eating too much relative to your training.