Weight Gain Calculator
Find the calorie surplus to gain weight or muscle at a steady pace, with a timeline to your goal.
About the Weight Gain Calculator
Gaining weight slowly, about 0.25 kg (0.5 lb) a week, keeps more of the gain as muscle when combined with strength training. Faster surpluses mostly add fat.
The plan adds a daily surplus to your maintenance calories, using about 7,700 kcal per kilogram of body weight.
The formula
Daily surplus = weekly gain (kg) × 7,700 ÷ 7
- Maintenance
- BMR (Mifflin-St Jeor) × activity factor
- Weeks
- weight difference ÷ weekly rate
Worked example
A 28-year-old man, 178 cm and 65 kg, moderately active, aiming for 72 kg at 0.25 kg a week
- Maintenance (Mifflin-St Jeor × 1.55): (10 × 65 + 6.25 × 178 − 5 × 28 + 5) × 1.55 = 2,523 kcal
- Daily surplus: 0.25 × 7,700 ÷ 7 = 275 kcal
- Eat about 2,798 kcal a day; 7 kg ÷ 0.25 kg a week = 28 weeks
Things to keep in mind
- This is an estimate for general information, not medical advice. Talk to a doctor or other qualified professional about your health.
- The 7,700 kcal/kg rule is a simplification; the NIH Body Weight Planner models adaptation more precisely.
Questions people ask
How do I gain muscle rather than fat?
Lift weights 3–4 times a week, eat 1.6–2.2 g of protein per kg and keep the surplus small.
Why so slow?
Muscle can only be built at a limited rate; extra calories beyond that are stored as fat.