To gain muscle, you need to eat about 10–20% more calories than your body burns each day. For most people, that works out to roughly 200–500 extra calories above your maintenance level. Eating too far above that range adds more body fat than muscle, while eating too little leaves your body without the raw materials it needs to build new tissue.
Finding Your Maintenance Calories
Before you can add a surplus, you need to know how many calories your body uses in a normal day. This number, called your Total Daily Energy Expenditure (TDEE), accounts for everything from breathing and digestion to walking and working out. The most widely used method to estimate it starts with a base metabolic rate formula, then adjusts for how active you are.
For men, the base 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. Once you have that number, you multiply it by an activity factor:
- 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
- Active (hard exercise 6–7 days/week): multiply by 1.725
- Very active (intense daily training or physical job): multiply by 1.9
As an example, a 28-year-old man who weighs 80 kg (176 lbs), stands 178 cm (5’10”), and lifts weights four days a week would calculate: (10 × 80) + (6.25 × 178) − (5 × 28) + 5 = 1,777.5. Multiplied by the moderately active factor of 1.55, that gives roughly 2,755 calories per day as a maintenance estimate. His muscle-building target would be about 3,030 to 3,305 calories.
These formulas are starting points, not gospel. Track your weight over two to three weeks at your estimated maintenance level. If your weight stays stable, you’ve found the right baseline. If it drifts up or down, adjust by 100–200 calories and recheck.
How Big Your Surplus Should Be
A good target is a weight gain of about 0.25–0.5% of your body weight per week. For someone weighing 180 lbs, that’s roughly 0.5 to 0.9 lbs per week. Gaining faster than that typically means you’re storing more fat than necessary.
Your training experience matters here. If you’re relatively new to lifting (less than six months of consistent training), your body can build muscle quickly, so aiming for the higher end of the 10–20% surplus makes sense. You’ll put on muscle fast enough to justify the extra calories. Experienced lifters should stay closer to the lower end, around 10%, because the rate of muscle growth slows with training age and a larger surplus just adds fat.
Protein: The Most Important Macro
Calories get you into a surplus, but protein is what your body actually uses to repair and build muscle fibers. People who lift regularly need 1.2 to 1.7 grams of protein per kilogram of body weight each day. For a 180 lb (82 kg) person, that’s roughly 98 to 139 grams of protein daily. Most people aiming for muscle growth do well targeting the upper end of that range.
Spreading your protein across three to four meals matters more than most people realize. After a resistance training session, your body ramps up the process of building new muscle protein for up to 48 hours. Having protein available throughout that window, not just in one massive post-workout shake, gives your body a steady supply of the amino acids it needs. Aim for 25–40 grams of protein per meal rather than cramming it all into one or two sittings.
Carbs and Fats Fill the Rest
Carbohydrates are the fuel your muscles burn during hard sets. When your muscle glycogen (stored carbohydrate energy) runs low, your performance drops, you can’t train as hard, and you lose the stimulus that triggers growth. Research on resistance training performance recommends 4–7 grams of carbohydrates per kilogram of body weight daily. For the same 82 kg person, that’s 328 to 574 grams per day. If you train three or four times a week at moderate intensity, the lower end of that range is plenty. If you train five or six days with high volume, push toward the higher end.
Good carbohydrate sources include rice, oats, potatoes, pasta, bread, and fruit. These are easy to eat in quantity and digest well around training. Timing a larger portion of your carbs before and after workouts can help performance and recovery, though total daily intake matters more than exact timing.
Fat fills in the remaining calories after protein and carbs are accounted for. Fat supports hormone production, including testosterone, which plays a direct role in muscle building. A floor of about 0.7–1 gram per kilogram of body weight keeps hormone levels healthy. In practice, once you’ve set your protein and carb targets, whatever calories are left should come from fat. Sources like olive oil, nuts, avocado, eggs, and fatty fish make it easy to hit the number without feeling stuffed.
Putting It Together: A Practical Example
Take that same 82 kg lifter with a maintenance of about 2,755 calories. Adding a 15% surplus brings the daily target to roughly 3,170 calories. Here’s one way to split the macros:
- Protein: 135 g (540 calories)
- Carbohydrates: 400 g (1,600 calories)
- Fat: 115 g (1,035 calories)
That totals about 3,175 calories. These numbers don’t need to be exact every day. Hitting within 100 calories of your target most days and keeping protein consistently high is what drives results over weeks and months.
Adjusting Over Time
Your calorie needs aren’t static. As you gain weight, your maintenance calories increase because there’s more tissue to fuel. Reassess every four to six weeks. If weight gain stalls, add another 100–150 calories. If you’re gaining faster than 0.5% of body weight per week and noticing more fat than you’d like, pull back by the same amount.
The scale alone doesn’t tell the full story. Take progress photos, track your lifts, and measure your waist. If your strength is going up and your waist isn’t ballooning, the surplus is working. If your waist is growing fast but your bench press hasn’t moved, you’re likely eating more than you need. Small, consistent adjustments every few weeks are far more effective than dramatic swings between eating everything in sight and cutting calories aggressively.