How the weight gain calorie calculator works
The weight gain calorie calculator estimates how many calories you need each day to add weight on purpose — not from random snacking, but from a planned, calculated surplus. It starts by finding your basal metabolic rate (BMR) with the Mifflin-St Jeor equation, multiplies by an activity factor to get your maintenance calories (TDEE), then adds a surplus sized to your chosen weekly gain rate. The protein target is set in the well-supported 1.6–2.2 g/kg band that helps that extra weight become muscle rather than fat.
The formula in plain English
- BMR (Mifflin-St Jeor):
10 × kg + 6.25 × cm − 5 × age + 5 (men) / − 161 (women) - TDEE: BMR × activity factor (1.2 sedentary up to 1.9 athlete)
- Surplus: roughly 7,700 calories per kg of body weight, divided over the week. A 0.25 kg/week target ≈ +275 kcal/day; 0.45 kg/week ≈ +500 kcal/day.
- Protein: about 1.8 g per kg of current body weight.
Lean bulking vs "dirty" bulking
The internet loves the idea of a "dirty bulk" — eat everything in sight and worry about the fat later. In practice this almost always leaves you holding a lot of body fat at the end with a smaller muscle gain than you expected, and a long cut to follow. A lean bulk does the opposite: a small, deliberate surplus (around +250 to +500 calories) paired with progressive strength training. The scale moves slowly — about half a kilo a week — but a much higher share of that gain is the muscle you wanted.
Why fast gain backfires
Muscle protein synthesis has a ceiling. Even a well-trained lifter builds at most around 0.25–0.5 kg of muscle per month; complete beginners can do roughly double that for a year or so. Eating an extra 1,500 calories a day cannot break that ceiling — it just hands the surplus to fat cells. Aim for a rate the calculator suggests, train hard, and let muscle accrue at its own pace.
Tracking the gain honestly
Weigh in once or twice a week at the same time of day and look at the 4-week trend. If you haven't gained at all in three weeks, add 100–150 calories. If you've gained noticeably faster than the target, drop 100. Don't change anything every day — weight bobs around by a kilogram or two from food, water and salt.
Pair with the rest of the toolkit
For a full macro split (protein, carbs and fat in grams), feed the same inputs into our macro calculator. To track what you're actually eating, the food calorie calculator turns a list of foods into a calorie total. For an everyday calorie need without the goal element, try the MyPlate calorie calculator.