Free weight-gain tool
Weight Gain Calculator
To gain weight you eat more than you burn. Enter your details to see your daily calories at a modest surplus, how fast that adds weight and how long a goal takes.
Worked example
For a 30-year-old man who weighs 75 kg and is 178 cm tall (lightly active), maintenance is 2,362 kcal. A 500 kcal daily surplus means eating about 2,862 kcal and gaining about 0.45 kg a week. Going from 75 kg to 80 kg at that pace takes about 11 weeks.
Calculate your calories to gain weight
The result below starts from the example's numbers. Change any field and it updates as you type.
Track this target every day
Use the number above as your daily goal in CalorTracker, then log meals by photo, voice or text and see where your day stands against it. Free to start, no card needed to explore.
Results are estimates from published formulas, not medical advice. Your own body can sit above or below them.
Where the formulas come from, and how we check them: how we calculate.
How the weight gain calculator works
It estimates your maintenance calories (TDEE, from the Mifflin-St Jeor equation and your activity level) and adds a daily surplus of 250 or 500 kcal. The weekly gain is the surplus times seven divided by about 7,700 kcal per kilogram.
The conversion is the old rule of thumb that a kilogram of body weight is worth about 7,700 kcal (about 3,500 kcal per pound), which goes back to Wishnofsky (1958). It is an average. Hall and colleagues (The Lancet, 2011) showed that real weight change settles lower than that rule predicts, because a lighter body burns less, so read any timeline here as the earliest sensible estimate and re-run it at your new weight.
Calorie surplus
A calorie surplus is eating more than you burn, and it is what this page calls the daily surplus. The two choices are the same +250 and +500 kcal steps in the TDEE calculator's goal table. A smaller surplus gains weight more slowly. Bulking is the same idea applied on purpose, usually alongside strength training.
What the weight is made of
The calculator counts calories, not tissue. How much of what you gain is muscle and how much is fat depends on your training, your protein intake and your own physiology, and no calculator can split it for you. If building muscle is the aim, the protein calculator and the macro calculator are the next stops.
If you are underweight, or have lost weight without meaning to, speak to a doctor before changing how you eat. This tool is not for anyone with a medical reason to gain weight.