Most people need to eat 250 to 500 calories above their maintenance level to bulk effectively. For a typical male weighing 170 pounds with moderate activity, that puts the target somewhere between 2,800 and 3,100 calories per day. But the right number for you depends on your current weight, activity level, and how long you’ve been training.
Find Your Maintenance Calories First
Before you can set a surplus, you need a baseline: the number of calories your body burns in a day just to maintain your current weight. The most reliable way to estimate this is the Mifflin-St Jeor equation, which a comparative study found predicts resting metabolic rate within 10% of measured values more often than other formulas.
For males, the formula is: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5. For females, it’s the same equation but minus 161 instead of plus 5. That gives you your resting metabolic rate, the calories your body burns doing absolutely nothing. To get your total daily energy expenditure (TDEE), multiply by an activity factor:
- Sedentary (desk job, no exercise): multiply by 1.2
- Lightly active (exercise 1–3 days/week): multiply by 1.375
- Moderately active (exercise 3–5 days/week): multiply by 1.55
- Very active (hard exercise 6–7 days/week): multiply by 1.725
A 25-year-old male who weighs 75 kg (165 lbs), stands 180 cm (5’11”), and lifts weights four days a week would calculate: (10 × 75) + (6.25 × 180) − (5 × 25) + 5 = 1,755 calories at rest. Multiply by 1.55 for moderate activity and you get roughly 2,720 calories per day as maintenance. That’s the starting point. Your bulking calories sit on top of that number.
How Big Your Surplus Should Be
A surplus of 250 to 500 calories per day is the standard range for most lifters. Where you land in that range depends largely on how much muscle you can still gain.
Beginners, or anyone who is still well below their genetic muscular potential, can handle a more aggressive approach. A 500-calorie surplus, aiming for roughly a pound of weight gain per week, works well during this phase because the body is primed to add muscle quickly. This “newbie gains” window means a higher proportion of the weight you gain will be muscle rather than fat, even at a larger surplus.
Intermediate and advanced lifters should be more conservative. When you’re closer to your muscular ceiling, muscle growth slows down, so extra calories beyond what your body can use for building tissue just get stored as fat. A surplus of 200 to 300 calories, targeting about half a pound of gain per week, is more appropriate. This is sometimes called a “lean bulk” and it keeps fat accumulation minimal while still providing enough energy for growth.
One important nuance: training experience matters less than how much room you have left to grow. Someone who has lifted casually for years but never followed a real program might still have plenty of untapped potential and can bulk more aggressively, just like a true beginner.
Why Your Body Resists a Big Surplus
You might assume that eating 500 extra calories means your body simply stores those 500 calories. It doesn’t work that cleanly. Your body adjusts its energy output in response to overfeeding, primarily through something called non-exercise activity thermogenesis, or NEAT. This includes all the small movements you make throughout the day: fidgeting, walking around, gesturing, even maintaining posture.
A well-known overfeeding study fed 16 young adults 1,000 extra calories per day for eight weeks. Two-thirds of the increase in their total daily energy expenditure came from increased NEAT. Some people’s NEAT rose by nearly 700 calories per day, essentially burning off most of the surplus without any deliberate exercise. Others barely changed at all. This variation in NEAT accounted for a tenfold difference in how much fat the participants stored.
The practical takeaway: if you eat a modest surplus and the scale doesn’t budge after two weeks, your body may be compensating by ramping up unconscious activity. You might need to increase your intake by another 100 to 200 calories and reassess. The number you calculate is always a starting point, not a fixed prescription.
Protein, Carbs, and Fat Ratios
Calories determine whether you gain weight. How you split those calories between protein, carbs, and fat determines how much of that weight is muscle.
Protein is the non-negotiable priority. People who lift regularly need 1.2 to 1.7 grams of protein per kilogram of body weight each day. For a 180-pound (82 kg) person, that’s roughly 100 to 140 grams of protein daily. Going above 2 grams per kilogram is generally considered excessive and doesn’t appear to offer additional muscle-building benefits.
A practical starting split for bulking is roughly 30 to 35 percent of calories from protein, 35 to 40 percent from carbohydrates, and about 30 percent from fat. For someone eating 3,000 calories a day, that looks like:
- Protein: 225–260 grams (900–1,050 calories)
- Carbohydrates: 260–300 grams (1,050–1,200 calories)
- Fat: 100 grams (900 calories)
Carbohydrates fuel your training sessions and help replenish muscle glycogen, so skimping on them during a bulk typically hurts performance in the gym. Fat supports hormone production, including testosterone, which plays a direct role in muscle growth. Dropping fat below about 20 percent of total calories for extended periods can interfere with hormonal balance.
Tracking Progress and Adjusting
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 weight fluctuates by 2 to 4 pounds based on water retention, sodium intake, and how much food is sitting in your digestive system. The weekly average smooths all of that out.
If your weekly average is climbing by about 0.5 to 1 pound per week (depending on your experience level), your surplus is in the right zone. If weight isn’t moving after two consistent weeks, add 150 to 250 calories. If you’re gaining faster than a pound per week and you’re not a complete beginner, you’re likely accumulating more fat than necessary. Pull back by 100 to 200 calories.
Your calorie target will also shift as you gain weight. Every 10 pounds of added body mass increases your maintenance calories, so a surplus that worked at 160 pounds may become maintenance at 175. Recalculate every 10 to 15 pounds or whenever the scale stalls for more than two weeks despite consistent eating.
A Quick Example
A 30-year-old woman, 5’6″ (168 cm), weighing 135 lbs (61 kg), lifting four days per week. Her resting metabolic rate using the Mifflin-St Jeor formula: (10 × 61) + (6.25 × 168) − (5 × 30) − 161 = 1,299 calories. Multiplied by 1.55 for moderate activity, her maintenance is about 2,013 calories. As an intermediate lifter, a 250-calorie surplus puts her target at roughly 2,260 calories per day, with around 90 to 100 grams of protein, 200+ grams of carbs, and 70 to 75 grams of fat.
A 22-year-old man, 6’0″ (183 cm), weighing 155 lbs (70 kg), new to lifting. Resting metabolic rate: (10 × 70) + (6.25 × 183) − (5 × 22) + 5 = 1,699 calories. With a 1.55 activity multiplier, maintenance is about 2,633 calories. As a beginner with significant room to grow, a 500-calorie surplus brings his target to approximately 3,130 calories per day, with 120 to 140 grams of protein as the foundation.