To gain muscle, most people need to eat roughly 200 to 500 calories above their maintenance level each day. There’s no single magic number that works for everyone, but you can get a reliable starting point by calculating your basal metabolic rate, multiplying it by an activity factor, and then adding a modest surplus on top. Here’s how to do that step by step.
Step 1: Calculate Your Basal Metabolic Rate
Your basal metabolic rate (BMR) is the number of calories your body burns just to stay alive: breathing, circulating blood, maintaining body temperature. It doesn’t account for any movement or exercise. The most widely recommended formula for estimating BMR is the Mifflin-St Jeor equation, which the Academy of Nutrition and Dietetics considers the most accurate option for healthy adults of various body sizes.
For men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
For women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
If you’re more comfortable with pounds and inches, convert first. Divide your weight in pounds by 2.2 to get kilograms, and multiply your height in inches by 2.54 to get centimeters. For example, a 30-year-old man who weighs 180 pounds (81.8 kg) and stands 5’10” (177.8 cm) would calculate: (10 × 81.8) + (6.25 × 177.8) – (5 × 30) + 5 = 1,782 calories per day as his BMR.
Step 2: Factor In Your Activity Level
Your BMR only reflects what you burn at rest. To find your total daily energy expenditure (TDEE), which is your actual maintenance calories, multiply your BMR by an activity multiplier:
- Sedentary (desk job, no exercise): BMR × 1.2
- Lightly active (light exercise 1-3 days/week): BMR × 1.375
- Moderately active (moderate exercise 3-5 days/week): BMR × 1.55
- Very active (hard exercise 6-7 days/week): BMR × 1.725
- Extremely active (physical job plus intense training): BMR × 1.9
Using the same 30-year-old man from above who lifts weights four days a week and walks regularly, the moderately active multiplier gives him a TDEE of roughly 2,762 calories (1,782 × 1.55). That’s his estimated maintenance, the number of calories where he’d neither gain nor lose weight.
Step 3: Add Your Caloric Surplus
Once you have your maintenance number, the general recommendation is to add 5 to 10 percent more calories on top. For someone maintaining at 2,762 calories, that means eating between 2,900 and 3,038 calories per day. This range is enough to fuel new muscle tissue without piling on unnecessary body fat.
Where you land within that range depends on your training experience. If you’re relatively new to lifting (less than a year of consistent training), your body can build muscle faster, so a surplus toward the higher end works well. Beginners can get away with eating more aggressively because a larger proportion of the weight they gain tends to be lean mass rather than fat. If you’ve been training seriously for several years, a smaller surplus of around 5 percent is more appropriate. Advanced lifters build muscle more slowly, so extra calories beyond what’s needed simply get stored as fat.
A Quick Example Calculation
Here’s the full process for a 25-year-old woman who weighs 140 pounds, stands 5’6″, and does resistance training four times per week:
Weight: 140 lbs ÷ 2.2 = 63.6 kg. Height: 66 inches × 2.54 = 167.6 cm.
BMR: (10 × 63.6) + (6.25 × 167.6) – (5 × 25) – 161 = 636 + 1,047.5 – 125 – 161 = 1,397.5 calories.
TDEE: 1,397.5 × 1.55 = 2,166 calories (maintenance).
Muscle gain target: 2,166 + 5 to 10% = roughly 2,275 to 2,383 calories per day.
Why a Moderate Surplus Works Better Than a Large One
Your body can only synthesize a limited amount of muscle tissue per day, no matter how much you eat. Once you’ve provided enough energy and protein to max out that process, every extra calorie gets stored as body fat. A surplus of 500 or more calories can make sense for underweight beginners trying to gain overall size, but for most people focused on building muscle with minimal fat gain, 200 to 400 extra calories hits the sweet spot.
There’s a popular idea in fitness circles that you should get lean before trying to bulk up, based on the theory that higher body fat impairs how your body partitions calories between muscle and fat. The research behind this is weaker than many people assume. The original model was based on observations of non-exercising individuals, some recovering from anorexia, and was never designed to guide bulking and cutting cycles for people who lift weights. Studies on sumo wrestlers, for instance, show that athletes at very high body fat levels continue to gain substantial lean mass as they progress through competition ranks. So while staying reasonably lean is fine for health and aesthetic reasons, you don’t need to diet down to a specific body fat percentage before you start eating in a surplus.
Protein, Carbs, and Fat Targets
Total calories matter most, but how you split those calories across protein, carbs, and fat affects your results. Protein is the biggest priority because it provides the building blocks for new muscle tissue. Aim for 0.7 to 1 gram of protein per pound of body weight per day. For the 180-pound man in our example, that’s 126 to 180 grams of protein daily.
Fat should make up roughly 25 to 35 percent of your total calories. Fat supports hormone production, including testosterone, which plays a direct role in muscle growth. At 3,000 calories, that’s about 83 to 117 grams of fat per day. Fill the remaining calories with carbohydrates. Carbs fuel your training sessions and help replenish the energy stores in your muscles afterward. For someone eating 3,000 calories with 160 grams of protein and 100 grams of fat, that leaves roughly 338 grams of carbs.
How to Tell If Your Surplus Is Working
Calculators give you a starting point, not a final answer. Your actual metabolism can vary from the formula’s estimate by 10 to 15 percent in either direction, so you need to track your results and adjust. Weigh yourself at the same time each morning for two weeks, then calculate the weekly average. If you’re gaining 0.25 to 0.5 pounds per week, you’re in a solid range for lean muscle gain. Beginners might gain closer to 0.5 to 0.75 pounds per week in the first few months.
If your weight isn’t moving after two weeks, add 100 to 150 calories per day and reassess. If you’re gaining faster than a pound per week (and you’re not a true beginner), you’re likely adding more fat than necessary. Pull back by 100 to 200 calories. Small adjustments every two to three weeks keep you on track without overcorrecting.
Strength gains in the gym are another useful signal. If your lifts are consistently going up and your weight is gradually increasing, your calorie intake is doing its job. If your strength stalls despite consistent training and sleep, calories or protein are the first things to look at.