By Zencalcy Editorial TeamLast reviewed About us
Gaining weight requires a sustained calorie surplus above maintenance. This calculator estimates maintenance from the Mifflin-St Jeor equation and an activity multiplier, then adds the surplus you choose. It also converts that surplus into an approximate weekly weight gain.
Calories and expected weekly gain for a controlled surplus.
Maintenance = BMR x activity multiplier Target = maintenance + surplus Weekly gain (kg) ~ surplus x 7 / 7700
The weekly gain estimate uses the same 7700 kcal per kilogram approximation as weight-loss tools. Part of a surplus can go to lean mass, fat and water, and the split depends on training, protein intake and genetics. The scale may move faster or slower than the projection.
| Symbol | Meaning |
|---|---|
| BMR | Basal metabolic rate in kilocalories per day. |
| surplus | Extra daily calories above maintenance. |
| target | Daily calorie intake for the selected surplus. |
| weekly gain | Approximate weight gain in kilograms per week. |
BMR is 1780 kcal and the moderate multiplier is 1.55, so maintenance is 2759 kcal per day. Adding a 500 kcal surplus gives a target of 3259 kcal per day. The expected gain is 500 x 7 / 7700 = 0.45 kg per week.
A calorie surplus supplies the energy for growth, but it does not decide what grows. Resistance training, sufficient protein and sleep create the conditions for lean tissue gain, while a very large surplus mostly increases fat storage. That is why a moderate surplus is usually easier to manage than a dramatic one. The weekly estimate from this calculator is a guide, not a contract. Track your weight as a weekly average, watch your waist and strength numbers, and adjust the surplus if the rate is much faster or slower than intended. If the scale is climbing quickly but strength is stagnant, the surplus may be larger than your training can use. If weight is flat for several weeks, a small increase in intake is a sensible next step.
Continue with the BMR Calculator (Mifflin-St Jeor), Harris-Benedict Calculator, or the Katch-McArdle Calculator — or browse more dietary tools and all health calculators.
Also see the Calorie Calculator, TDEE Calculator and the Macro Calculator.
A surplus of 250 to 500 kcal per day is a reasonable starting range for many people. Larger surpluses can speed the scale up but often add more fat. Choose a size you can sustain and adjust from the weight trend.
Energy and nutrient estimates are population guidance, not personal prescriptions. Actual needs vary with body composition, medical conditions, medication, pregnancy and activity. Values are rounded and should be discussed with a registered dietitian or clinician when used to plan treatment.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
Content updated: September 2026