To build muscle, you need to eat about 5 to 20% more calories than your body burns each day. For someone maintaining their weight on 2,000 calories, that means eating 2,100 to 2,400 calories daily. The exact number depends on your body size, how active you are, and how long you’ve been lifting.
Getting this number right matters. Eat too little and your body won’t have the raw materials to add new tissue. Eat too much and the extra calories get stored as fat, not muscle. Here’s how to find your target.
Find Your Maintenance Calories First
Before you can calculate a surplus, you need to know how many calories your body burns in a normal day. This is called your total daily energy expenditure, and it has three parts: your resting metabolic rate (the calories your body burns just keeping you alive), the energy you burn through physical activity, and the calories spent digesting food. Your resting metabolism alone accounts for 60 to 70% of your daily calorie burn. Digestion handles about 10%. Everything else comes from movement.
The simplest way to estimate your maintenance calories is to start with your resting metabolic rate and multiply it by an activity factor. Most online calculators do this for you, but the multipliers look like this:
- Sedentary (desk job, no exercise): multiply by 1.2
- Somewhat active (light exercise 1 to 3 days per week): multiply by 1.3 to 1.4
- Active (moderate exercise 4 to 5 days per week): multiply by 1.5
- Very active (hard training 6+ days per week): multiply by 1.6 to 1.7
If you’re a 170-pound man with a resting metabolic rate of about 1,800 calories and you train four days a week, your estimated maintenance sits around 2,700 calories (1,800 × 1.5). A 140-pound woman with a resting rate of 1,400 and similar activity would land near 2,100.
These are estimates. The most reliable way to confirm your maintenance number is to track your weight for two weeks while eating consistently. If your weight stays stable, that’s your maintenance intake.
How Big Your Surplus Should Be
A surplus of 5 to 20% above maintenance builds muscle while keeping fat gain in check. On the conservative end, that’s an extra 100 to 150 calories per day. On the higher end, it’s closer to 400 to 500. Where you land in that range depends mostly on your training experience.
If you’re new to lifting, your body responds aggressively to the stimulus. Beginners can build muscle faster than experienced lifters, so a surplus of around 500 calories (roughly a pound of weight gain per week) is reasonable. Your body has a lot of room to grow, and more of those extra calories will go toward muscle rather than fat.
If you’ve been training consistently for a year or more, a smaller surplus is smarter. Experienced lifters build muscle more slowly, so a large surplus just adds body fat. Sticking closer to the 5 to 10% range (150 to 250 extra calories) makes sense. The further you are from your genetic muscular potential, the faster you can grow. As you get closer, progress slows and precision matters more.
Starting on the low end and adjusting upward is almost always better than starting high. You can increase your intake by 100 to 200 calories if you’re not seeing progress after a few weeks.
Why Your Body Needs Extra Calories
Building muscle tissue is an energy-expensive process. Your body has to synthesize new proteins, repair damaged fibers, and support all the metabolic activity that comes with adding lean mass. Research on tissue synthesis suggests it costs roughly 8 to 9 calories to deposit a single gram of new protein in the body. Since a pound of muscle is only about 20% protein (the rest is water and other components), the total energy cost of building a pound of muscle is lower than you might expect, but your body still needs a sustained energy surplus to prioritize growth over other metabolic demands.
Without that surplus, your body tends to direct available calories toward maintaining what it already has. You can build some muscle eating at maintenance, especially as a beginner, but a deliberate surplus sends a stronger signal that your body has the resources to add new tissue.
Protein, Carbs, and Fat Targets
Total calories matter most, but where those calories come from affects how much of your weight gain is muscle versus fat.
Protein
Protein is the building block of muscle tissue and the nutrient most people focus on. The current recommendation for active people doing resistance training is 1.4 to 2 grams of protein per kilogram of body weight per day. For a 180-pound person, that works out to about 115 to 165 grams daily. Spreading this across meals (20 to 40 grams per meal) supports a more consistent rate of muscle protein synthesis throughout the day.
Carbohydrates
Carbs fuel your training sessions and help your muscles recover afterward. The International Society of Sports Nutrition recommends active individuals consume 5 to 8 grams of carbohydrates per kilogram of body weight daily to maintain energy stores in the muscles and liver. For a 180-pound person, that’s roughly 400 to 650 grams. If you’re training hard for over two hours a day, that number can climb higher, but most people lifting weights four to five days a week will fall in the lower half of that range.
Skimping on carbs leaves you sluggish in the gym. Sluggish training means less mechanical tension on your muscles, which means a weaker growth signal regardless of how many calories you eat.
Fat
After hitting your protein and carb targets, fill the remaining calories with dietary fat. Fat supports hormone production (including testosterone, which plays a role in muscle growth) and helps you absorb certain vitamins. Most people land somewhere between 20 and 35% of total calories from fat, which works well for a muscle-building diet.
A Practical Example
A 175-pound man who trains four days per week might estimate his maintenance at roughly 2,700 calories. Starting with a moderate 15% surplus puts his target at about 3,100 calories. His macronutrient breakdown could look like this: 160 grams of protein (640 calories), 450 grams of carbohydrates (1,800 calories), and 75 grams of fat (675 calories), totaling about 3,115 calories.
A 140-pound woman with the same training schedule might maintain at around 2,100 calories. A 15% surplus brings her to roughly 2,400 calories. She might aim for 115 grams of protein, 330 grams of carbohydrates, and 60 grams of fat.
These are starting points. The real work is in tracking what happens next.
How to Adjust Over Time
Weigh yourself at the same time each day (morning, after using the bathroom) and track your weekly average. This smooths out the daily fluctuations from water, food volume, and sodium that can make individual weigh-ins misleading.
If you’re a beginner, aim for about 0.5 to 1 pound of weight gain per week. If you’re more experienced, 0.5 pounds per week or even less is appropriate. Gaining faster than this usually means you’re adding more fat than necessary.
If your weight isn’t moving upward after two to three weeks, add 100 to 200 calories to your daily intake. If you’re gaining faster than expected and noticing more fat accumulation than you’d like, reduce by the same amount. Small, patient adjustments beat dramatic overhauls. Your metabolism adapts to changes in intake, and the calorie target that works in month one may need a bump by month three as your body gets heavier and your activity increases.
Body composition changes also matter more than the scale alone. Progress photos taken every few weeks and strength gains in the gym are better indicators of whether your surplus is doing its job than weight alone. If you’re getting stronger and your body looks more muscular, the plan is working even if the scale moves slowly.