Calorie Calculator for Weight Gain
Struggling to put on weight? Find the calorie surplus that adds size steadily, and see a 12-week projection of your progress update as you adjust.
Your details
How your surplus is built
12-week weight projection
Estimated gain at this surplus (7,700 kcal ≈ 1 kg).
Gaining weight is the mirror image of losing it: eat more calories than you burn, and your body stores the surplus. This calculator finds your maintenance level, adds the surplus you choose, and projects your weight gain over twelve weeks. A modest surplus of 250–500 calories is usually enough — piling on far more just adds fat faster than your body can turn it into muscle.
How much of a surplus do you need to gain weight?
To gain weight you need to eat above your TDEE. A surplus of around 250 calories a day supports a slow, lean gain of roughly half a pound (0.25 kg) per week — ideal if you want to minimise fat. A 500-calorie surplus produces about a pound a week and suits hard-gainers who struggle to move the scale at all.
The Energy Flow diagram shows how your surplus stacks on top of your BMR and activity, and the projection line forecasts your gain week by week. Adjust the surplus and both respond instantly so you can pick a pace you're comfortable with.
Gaining weight without gaining excess fat
Bigger surpluses don't build muscle faster — your body can only assemble new muscle at a limited rate, so anything beyond that is stored as fat. That's why a controlled surplus paired with resistance training gives the best ratio of muscle to fat. If you're training to build muscle specifically, our muscle-gain calculator adds a protein-forward macro breakdown on top of these numbers.
Track your weight weekly. If you're gaining faster than about 0.5–1% of your bodyweight per week, trim the surplus; if the scale isn't moving after two weeks, nudge it up by 100–200 calories.
Frequently Asked Questions
Eat 250–500 calories above your TDEE. Use the calculator to get your personalised surplus based on your age, sex, height, weight, and activity level.
A 250-calorie surplus adds roughly half a pound (0.25 kg) per week, and a 500-calorie surplus about a pound. Gains beyond that are usually mostly fat and water rather than muscle.
A surplus provides the energy to build muscle, but you also need resistance training and enough protein to turn those calories into lean mass. Without training, most of a surplus becomes fat.
Slowly. A modest surplus keeps the fat-to-muscle ratio favourable and is easier on digestion and appetite. Aggressive bulking mostly adds fat you'll later have to diet off.
Yes. As you get heavier your maintenance calories rise, so re-enter your weight every few weeks to keep your surplus on target.
These results are estimates for general educational purposes only and are not medical or nutritional advice. Individual needs vary. Consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, especially if you are pregnant, breastfeeding, under 18, or have a medical condition.