How much to eat to gain weight
Gaining weight comes down to one rule: eat more calories than you burn. Your body spends a certain amount each day to stay alive and move around, called total daily energy expenditure, or TDEE. Eat above that figure and the extra energy is stored, some as muscle and some as fat. The gap between what you burn and what you eat is the surplus.
This calculator estimates your TDEE from your height, weight, age, sex, and activity, then adds a surplus sized to your chosen gain rate. The TDEE calculator shows the maintenance figure on its own if you want to see it first.
Choosing a gain rate
The surplus rests on a well-worn proxy: about 7,700 calories per kilogram of body tissue, close to 3,500 per pound. Spread across a week, that sets the daily surplus for a target rate.
| Gain rate | Daily surplus | Weekly gain |
|---|---|---|
| Lean gain | About 275 kcal | 0.25 kg (0.5 lb) |
| Faster gain | About 550 kcal | 0.5 kg (1 lb) |
A smaller surplus of roughly 250 to 300 calories, giving about a quarter kilo a week, puts the most of the gain into muscle and the least into fat. A larger surplus fills the scale faster, but the part beyond what muscle can use is stored as fat. Unless you are very underweight, the leaner rate is the one worth defaulting to.
Protein and training decide the result
A surplus sets how fast the scale moves. Protein and resistance training set how much of that gain is muscle rather than fat. Aim for roughly 1.6 to 2.2 grams of protein per kilogram of body weight a day, and train the major muscle groups with progressive overload. The protein calculator sets the grams, and the macro calculator divides your gain calories across protein, carbs, and fat.
The mirror of a calorie deficit
Gaining and losing weight run on the same equation from opposite directions. A surplus above maintenance builds weight; a deficit below it takes weight off. Both lean on the same 7,700 calories per kilogram figure, so the sums look familiar either way. If your goal flips, the calorie deficit calculator runs the losing side with the same logic.
Whichever way you go, judge it by the trend on the scale over two to three weeks rather than any single day. Water, food weight, and normal swings hide the real change until you average them out. Adjust the surplus by 100 to 150 calories once the weekly average tells you whether you are on track. These figures are estimates, not medical advice; a doctor or dietitian can help if you are underweight or gaining for a health reason.
