Get your weight gain calorie target in seconds
Enter your stats and activity level to get a daily calorie target and an estimated timeline to your goal weight.
Activity levels explained
Your activity level sets the multiplier used to turn your BMR into your total daily energy expenditure (TDEE).
| Activity level | Multiplier | Description |
|---|---|---|
| Sedentary | × 1.2 | Little or no exercise |
| Lightly active | × 1.375 | Light exercise 1–3 days a week |
| Moderately active | × 1.55 | Moderate exercise 3–5 days a week |
| Active | × 1.725 | Hard exercise 6–7 days a week |
| Very active | × 1.9 | Very hard exercise or a physical job |
Not sure which one fits? Use the weight gain calculator above and try a couple — your calorie target updates instantly.
About this weight gain calculator
This calculator estimates your Basal Metabolic Rate (BMR) using the Mifflin–St Jeor equation, then multiplies it by an activity factor to get your Total Daily Energy Expenditure (TDEE) — the calories you burn maintaining your current weight.
From there, it applies a moderate 500-calorie daily surplus, based on the standard estimate that roughly 7,700 calories equals 1 kg of body weight. That works out to about 0.45 kg (1 lb) of weight gain per week — a pace that favors lean mass over rapid fat gain.
This is an estimate, not medical advice. How much of the gain becomes muscle depends on resistance training and protein intake, and individual metabolism varies. Talk to a doctor or dietitian before making major changes to your diet.
Sample weight gain timelines
Common starting weights and goals, already calculated.
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Female
Weight gain questions
How the calorie target and timeline are calculated.
How many calories should I eat to gain weight?
A common, sustainable approach is eating about 500 calories a day above your maintenance level (TDEE). That works out to roughly 0.5 kg (about 1 lb) of weight gain per week — enough to build mass without excessive fat gain.
How is my calorie target calculated?
This calculator estimates your Basal Metabolic Rate (BMR) using the Mifflin–St Jeor equation, multiplies it by your activity level to get your Total Daily Energy Expenditure (TDEE), then adds a 500-calorie daily surplus.
How long will it take to reach my goal weight?
Using the standard estimate that 1 kg of body weight is roughly 7,700 calories, a 500-calorie daily surplus works out to about 0.45 kg (1 lb) gained per week. Divide your total weight to gain by that weekly rate to estimate the number of weeks.
Will a calorie surplus all turn into muscle?
No — how much of the gain is muscle versus fat depends heavily on strength training and protein intake. Without resistance training, most of a calorie surplus is stored as fat.
Why does activity level matter for weight gain?
Your activity level changes your TDEE — more active people burn more at maintenance, so they need a higher calorie target to hit the same 500-calorie surplus.
Is it better to gain weight slowly?
Yes, for most people. A moderate surplus like the one used here helps minimize fat gain relative to muscle, especially when combined with resistance training and enough protein.