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Calculator Answers

Weight Gain Calculator

Source: Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247 · Source verified July 22, 2026

Blake Boege
Written by Blake Boege · Founder, Calculator Answers

Weight gain occurs when daily caloric intake consistently exceeds Total Daily Energy Expenditure (TDEE), creating a calorie surplus. A weight gain calculator estimates the daily calorie surplus required to gain weight at a target weekly rate the user chooses, since no named body publishes a safe rate of weight gain for adults. It calculates Basal Metabolic Rate (BMR) via the Mifflin-St Jeor equation, estimates TDEE based on physical activity level, and adds the surplus calories needed. Fitness professionals, athletes, and underweight individuals use this calculation to structure clean bulks or nutritional therapy programs.

Estimate the daily calorie surplus and total daily calories needed to gain weight at a target weekly rate. Uses the Mifflin-St Jeor BMR formula and activity multipliers.

See also: Calorie Deficit Calculator, TDEE Calculator, and BMI Calculator.

Quick Answer

Find the daily calories required to gain weight at a target weekly rate. Enter your age, sex, height, weight, activity level, and weight gain rate to calculate your target calorie intake.

Profile details

Sex (for BMR formula)

Units

lb
Height
ft
in

Activity level

lb/wk

The rate you want. No body publishes a safe rate of gain; this is the figure the arithmetic works from.

Gain projection

Daily Calorie Target

2,841 kcal/day

TDEE 2,591 kcal + Surplus 250 kcal

BMR (resting metabolic rate)1,672 kcal
TDEE (maintenance calories)2,591 kcal
Weekly Gain Rate Goal0.5 lb/week
Daily Calorie Surplus+250 kcal
Daily Calorie Target2,841 kcal/day

* Estimate, not medical advice. Individual results vary based on metabolism, body composition, sleep, hydration, and exercise habits.

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Examples

Male, 25, 150 lbs, 5'10", Moderately Active, +0.5 lb/wk

TDEE ≈ 2,450 kcal, Target ≈ 2,700 kcal/day

Female, 30, 110 lbs, 5'4", Lightly Active, +0.25 lb/wk

TDEE ≈ 1,650 kcal, Target ≈ 1,775 kcal/day

Male, 21, 70 kg, 180 cm, Sedentary, +0.5 kg/wk

TDEE ≈ 2,050 kcal, Target ≈ 2,600 kcal/day

How it works

Formula · BMR (male) = 10 × weight kg + 6.25 × height cm − 5 × age + 5; BMR (female) = 10 × weight kg + 6.25 × height cm − 5 × age − 161

The weight gain calculator estimates your maintenance calories (TDEE) using the Mifflin-St Jeor equation and physical activity multipliers. It then calculates the required daily surplus: 3,500 calories per pound of target gain, or 7,700 calories per kilogram of target gain, divided over 7 days. Those two figures are round conventions rather than a matched pair: 3,500 per pound works out to about 7,716 per kilogram, so the same goal entered in the two units differs by a fraction of a percent. The larger caveat is that the conversion is static. It comes from a 1958 paper and assumes the exchange rate between calories and body weight never changes, when energy needs in fact fall as body mass changes, so a fixed daily surplus produces less change over time than a straight multiplication suggests.

Mifflin-St Jeor (BMR) · Men: 10·wt(kg) + 6.25·ht(cm) − 5·age + 5

Mifflin-St Jeor (BMR) · Women: 10·wt(kg) + 6.25·ht(cm) − 5·age − 161

TDEE · TDEE = BMR × Activity Multiplier

Daily Calorie Target · Target = TDEE + (Target Surplus/Week × Calories Per Unit / 7)

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More tools from Health

Calorie Deficit CalculatorWork out a daily calorie deficit from your maintenance estimate and intake, or the intake that produces a deficit you choose. Also plans backwards from a target weight by date or weekly rate.TDEE CalculatorEstimate your Total Daily Energy Expenditure from sex, age, height, weight, and activity — with maintenance, cut, and bulk targets.BMI CalculatorCompute Body Mass Index from height and weight, with the standard category scale and the healthy weight range for your height.

Frequently asked questions

The arithmetic is a surplus above maintenance, and this page will do that arithmetic for you: at the static 3,500 calories per pound conversion, 250 calories a day is 0.5 lb a week and 500 a day is 1.0 lb a week. What this page will not do is tell you which to pick. One named body does publish a figure, for a different question: the NHS tells underweight adults they "could try adding around 300 to 500 extra calories a day", which is about gaining weight generally rather than gaining muscle, and note that it is 300 to 500 rather than the 250 to 500 that circulates. For MUSCLE gain specifically no body gives a number: the ISSN position stand on diets and body composition declines to name one and says the magnitude depends on training status, and the ACSM, Academy of Nutrition and Dietetics and Dietitians of Canada joint position stand publishes no daily surplus either. The nearest published figures are a percentage of maintenance rather than a fixed count. The 250 to 500 range that circulates, and that this page used to call typically recommended, is not traceable to a source. Intake above maintenance is what produces a surplus; whether any particular surplus suits you is a judgement this page holds no information to make.

BMR (Basal Metabolic Rate) is the baseline number of calories your body burns at rest to keep you alive. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by your physical activity level. Your TDEE is the 'maintenance' calorie count you must exceed to gain weight.

The calculator estimates your BMR using the Mifflin-St Jeor equation (based on age, sex, weight, and height). It multiplies BMR by your physical activity factor to estimate TDEE. Finally, it adds the surplus calories needed to achieve your target weekly rate of gain (assuming 1 pound of weight gain requires a total surplus of ~3,500 calories).

This page does not have an answer to that, and it previously gave three different ones. It said a 250 to 500 calorie surplus was recommended, which is 0.5 to 1.0 lb a week; it separately called 0.25 to 0.5 lb a week ideal; and the rate field described 0.25 to 1.0 lb a week as a typical safe range. Those are three different claims about the same quantity on one page. No named body publishes a safe or ideal rate of weight GAIN for adults, unlike weight loss where NHLBI and AHA both publish rates. Those loss figures are dated: the NHLBI numbers are its 1998 obesity report, which the 2013 AHA/ACC/TOS guideline updated with different ones, and both sets appear on this page rather than being blended. What is true is the mechanism: a faster gain adds a larger share of fat, and the split between lean and fat tissue depends on training and protein intake, which this equation does not model.

Focus on nutrient-dense, calorie-dense foods (nuts, seeds, avocados, whole grains, and lean proteins). Ensure you consume adequate protein (typically 0.8 to 1.0 gram per pound of body weight) and combine your diet with resistance training to promote muscle growth.