Short answer
A calorie surplus is eating more than your maintenance calories. Adding 300 calories a day suggests about 0.27 kg (0.6 lb) of weight gain a week, part of which may be water.
1. The formula
Calorie surplus = calories eaten − maintenance calories. Weekly gain = daily surplus × 7 ÷ 7,700 in kilograms. That is the same 7,700-calories-per-kilogram rule used for weight loss, so it gives an estimate, not a promise.
2. What each surplus does
The target column uses a man whose maintenance is 2,396 calories.
| Daily surplus | Weekly change | Daily target |
|---|---|---|
| 250 calories | about 0.23 kg (0.5 lb) | 2,646 |
| 300 calories | about 0.27 kg (0.6 lb) | 2,696 |
| 500 calories | about 0.45 kg (1 lb) | 2,896 |
| 750 calories | about 0.68 kg (1.5 lb) | 3,146 |
3. Worked example
A 25-year-old man, 70 kg and 180 cm, moderately active, has a BMR of 10 × 70 + 6.25 × 180 − 5 × 25 + 5 = 1,705 calories. Multiplied by 1.55, his maintenance is about 2,643. A 300-calorie surplus gives a target of about 2,943 calories a day.
4. Keeping the gain mostly lean
- Pair the surplus with strength training. Without it, more of the gain is likely to be fat.
- Keep protein high. The Calorie Calculator uses 1.8 g per kg of body weight when your goal is to gain.
- Keep the surplus modest. A bigger surplus than you need usually adds more fat, not faster muscle.
5. Adjusting along the way
Weigh yourself at the same time of day and compare weekly averages. If your weight has not moved after two to three weeks, add 100 to 200 calories. If it rises faster than you want, take some away.
6. Frequently asked questions
How many calories should I add to gain weight?expand_more
A surplus of 250 to 500 calories above maintenance is a common range for gradual gain. Start at the lower end and adjust based on your weekly average weight.
How much weight will I gain from a 500-calorie surplus?expand_more
About 0.45 kg (1 lb) a week by the 7,700-calories-per-kilogram rule. Part of that can be water, and only part will be muscle.
Do I need to eat more if I want to build muscle?expand_more
Usually yes, a modest surplus helps, together with strength training and enough protein. Without training, extra calories are more likely to be stored as fat.
How do I find my maintenance calories?expand_more
Enter your sex, age, height, weight and activity level in the Calorie Calculator. Then add your surplus to the maintenance figure.