To build muscle, most people need to eat about 5 to 20% more calories than their body burns in a 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, training experience, and how aggressively you want to gain.
Getting this number right matters more than most people realize. Eat too little and your body won’t have the raw materials to add new tissue. Eat too much and you’ll gain muscle, sure, but buried under unnecessary fat. Here’s how to find your target and dial it in.
Find Your Maintenance Calories First
Before you can calculate a surplus, you need to know your baseline: the number of calories your body burns in a typical day just to maintain your current weight. This is called your total daily energy expenditure, or TDEE. It accounts for everything from breathing and digestion to walking around and working out.
The most practical way to estimate it is with a two-step process. First, calculate your basal metabolic rate (the calories your body burns at complete rest) using the Mifflin-St Jeor equation, which is the standard used in most clinical and sports nutrition settings:
- Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age) – 161
Then multiply that number by an activity factor to account for how much you move each day. Someone with a desk job who trains three or four days a week would use 1.55 (moderately active). A construction worker who also lifts would use 1.725 (active). The full scale runs from 1.2 for sedentary up to 1.9 for very active.
For example, a 30-year-old man who weighs 180 pounds (82 kg), stands 5’10” (178 cm), and trains four days a week would calculate: (10 × 82) + (6.25 × 178) – (5 × 30) + 5 = 1,783 calories at rest. Multiply by 1.55 and his estimated TDEE is roughly 2,764 calories per day.
These formulas are estimates, not gospel. The best way to verify is to eat at your calculated maintenance for two weeks, weigh yourself daily, and see if your average weight stays stable. If it drifts up, your true maintenance is a bit lower. If it drifts down, it’s higher. Adjust by 100 to 200 calories and retest.
How Much of a Surplus You Actually Need
A surplus of 5 to 20% above maintenance is the range that consistently supports muscle growth while keeping fat gain reasonable. The lower end (5 to 10%) works well for people who’ve been training for a year or more, since experienced lifters build muscle more slowly and a large surplus just gets stored as fat. The higher end (15 to 20%) is more appropriate for true beginners, who can add muscle quickly enough to actually use those extra calories.
In absolute terms, that usually translates to 200 to 500 extra calories per day for most people. Going much beyond that doesn’t speed up muscle growth. One study overfed resistance-trained men by roughly 1,250 calories per day for eight weeks. They did gain lean mass, but they also gained significant fat, and their body composition didn’t end up any better than it would have with a smaller surplus.
A conservative surplus is especially important for women. Research on resistance-trained female athletes suggests starting with a small surplus and adequate protein to maximize muscle gain while avoiding excessive fat accumulation. The principle is the same for everyone: your body can only synthesize a limited amount of muscle tissue per day, and extra calories beyond that ceiling get stored as fat.
Protein, Carbs, and Fat Targets
Calories get you into a surplus, but how you divide those calories between protein, carbohydrates, and fat determines what your body does with them.
Protein is the building block. The American College of Sports Medicine recommends 1.2 to 1.7 grams of protein per kilogram of body weight per day for people who train regularly. If you’re specifically trying to maximize muscle gain, aim for the higher end of that range. For a 180-pound (82 kg) person, that’s roughly 100 to 140 grams of protein daily. Spread it across three to five meals, since your body uses protein most efficiently in doses of about 25 to 40 grams at a time.
Carbohydrates fuel your workouts. Your muscles store carbs as glycogen, which is the primary energy source during resistance training. To support high training volumes, research recommends 4 to 7 grams of carbohydrates per kilogram of body weight per day. For that same 180-pound person, that’s 328 to 574 grams. If you train three to four days a week at moderate intensity, the lower end is sufficient. If you’re training five or six days with high volume, push toward the higher end.
Fat fills in the remaining calories and supports hormone production, including testosterone, which plays a role in muscle growth. Most people do well getting 20 to 35% of their total calories from fat. There’s no need to go lower than that, and doing so can actually interfere with hormonal balance.
A Practical Example
Take that 180-pound, moderately active man with a TDEE of about 2,764 calories. A 15% surplus puts him at roughly 3,180 calories per day. Here’s how that might break down:
- Protein: 140 grams (560 calories)
- Fat: 85 grams (765 calories)
- Carbohydrates: 464 grams (1,855 calories)
That’s not a rigid prescription. You can shift the ratio a bit based on personal preference, as long as protein stays high enough and carbs remain sufficient to fuel your training. Some people feel better with slightly more fat and fewer carbs, and that’s fine. The surplus itself and the protein target are the two variables that matter most.
How Fast You Should Gain Weight
Aim to gain no more than about one pound per week. If the scale is climbing faster than that, you’re likely adding more fat than muscle. For experienced lifters, even half a pound per week is a realistic target, since the rate of muscle gain slows considerably after your first year or two of training.
Weigh yourself daily at the same time (first thing in the morning, after using the bathroom) and look at your weekly average. Day-to-day fluctuations of one to three pounds are completely normal and driven by water, sodium, and digestive contents. The weekly trend is what matters. If your average weight isn’t moving up after two weeks, add another 100 to 150 calories per day. If it’s moving up too fast, pull back by the same amount.
Can You Build Muscle Without a Surplus?
Yes, but only under specific conditions. People who are new to resistance training, returning after a long break, or carrying significant body fat can often build muscle while eating at maintenance or even in a slight deficit. This process, sometimes called body recomposition, works because the body has enough stored energy (fat) to redirect toward muscle repair and growth while also tapping into that fat for fuel.
The tradeoff is speed. Recomposition is slower than a dedicated surplus for building muscle. If you’ve been training consistently for a year or more and you’re already relatively lean, a caloric surplus is the more effective path. But if you’re a beginner who also wants to lose some fat, you don’t need to force-feed yourself. Prioritize protein intake, train hard, and let your body do both jobs simultaneously.
Adjusting Over Time
Your calorie target isn’t something you set once and forget. As you gain weight, your maintenance calories increase because there’s simply more of you to fuel. Every 5 to 10 pounds you gain, recalculate your TDEE and adjust your surplus accordingly. Most people need to bump their intake by 100 to 200 calories every couple of months during a building phase.
Training adaptations matter too. If you increase your workout frequency or volume, your energy expenditure goes up, which means you may need more food to stay in a surplus. Conversely, during a deload week or a period of lower activity, you can pull calories back slightly to avoid unnecessary fat gain. The goal is to keep your rate of weight gain steady and deliberate rather than letting it drift in either direction.