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Weight Gain Calorie Calculator

Enter your details, activity level and a preferred calorie surplus to see a suggested daily calorie target, your estimated maintenance calories, and the estimated initial weekly gain.

Your details

Sex
years
This calculator is for adults aged 18 and over.
Before we calculate — do any of these apply?
If you tick any of these, the calculator will not set a surplus target and will point you to tailored advice instead.
Suggested daily calorie target
3,050 kcal/day
Estimated maintenance calories
2,550 kcal/day
Daily surplus
+500 kcal/day
Estimated initial weekly gain
0.45 kg/week (1.00 lb/week)

Your maintenance calories are an estimate based on your details and chosen activity level. Track your average calorie intake and your weight trend for 2–4 weeks, then adjust your surplus if needed. Actual scale weight varies with water, digestion, glycogen and normal day-to-day fluctuation, so treat the weekly gain as an initial estimate rather than a guarantee — and it is not muscle alone.

Estimate only. Calorie needs vary with body composition, daily movement, training, health and other factors. This is not medical advice or a meal plan. If you are pregnant, breastfeeding, under 18, or have a medical condition that affects your diet or weight, speak to a healthcare professional or registered dietitian before using calorie targets. Larger calorie surpluses may not be suitable for everyone, especially older adults or people with health conditions.

How to use this calculator

  1. Pick your sex, enter your age, height and weight.
  2. Choose the activity level that best reflects your typical week.
  3. Choose a preferred calorie surplus, or select "Custom surplus" to set your own.
  4. Read your suggested daily calorie target, maintenance calories, and estimated initial weekly gain.

Nothing is submitted anywhere. The calculation runs in the page as you type, and the link in your address bar carries your figures, so it can be shared or bookmarked.

How is the calorie target calculated?

Calorie target = BMR × Activity multiplier + Daily surplus
  • Estimated initial weekly gain (kg) = Daily surplus × 7 ÷ 7,700

Worked example. A 25-year-old, 178 cm, 65 kg man with moderate activity has a BMR of 1,642.5 kcal/day and estimated maintenance calories of 1,642.5 × 1.55 = 2,550 kcal/day. Adding the Standard gain +500 kcal/day surplus gives a target of 3,050 kcal/day, for an estimated initial gain of 500 × 7 ÷ 7,700 = 0.45 kg/week (1.00 lb/week).

Related tools

Want the raw BMR figure by itself? Use the BMR calculator. Splitting your calorie target into protein, carbs and fat? Use the macro calculator. Tracking progress against your starting weight? Use the weight change calculator.

Frequently asked questions

What is a weight gain calorie calculator?

It suggests a daily calorie target for gaining weight, from your estimated maintenance calories (BMR scaled by activity level) plus a chosen calorie surplus. It also shows the estimated initial weekly gain that surplus should produce.

How is the calorie target calculated?

BMR comes from the Mifflin–St Jeor equation, scaled up by your usual activity level to estimate maintenance calories (TDEE) — the same calculation the maintenance calories calculator uses. A chosen daily surplus is then added on top to give your calorie target.

How much weight will a given surplus add per week?

Estimated initial weekly change (kg) = daily calorie surplus × 7 ÷ 7,700. This calculator uses 7,700 kcal per kilogram, the same planning figure the weight loss calorie calculator uses. Real weight change is never this tidy — gained tissue is a shifting mix of muscle, fat and water — so treat the weekly figure as an initial estimate, not a guarantee, and not as muscle alone.

Which calorie surplus should I choose?

Gentle gain (+250 kcal/day) favours a slower gain with a higher share of muscle. Standard gain (+500 kcal/day) is a common general-purpose surplus. Higher surplus (+750 kcal/day) gains faster but tends to add more fat along with muscle, so the calculator shows a short neutral caution for surpluses above 500 kcal/day. A surplus above 750 kcal/day is not offered as a general target — the calculator points you to personalised advice instead.

Can I set my own surplus instead of a preset?

Yes — choose "Custom surplus" and enter any daily figure greater than 0. Values up to 750 kcal/day return an ordinary result; values above 750 and up to 1,000 kcal/day route to personalised advice; values above 1,000 kcal/day are not accepted.

Why won’t the calculator show me a target?

To keep the result suitable for general use, the calculator does not set a calorie-surplus target when you are under 18, when you tick one of the health questions (pregnancy or breastfeeding, a relevant health condition, medication or prescribed diet, or a current or past eating disorder), when a custom surplus is above 750 kcal/day, or when you are 65 or older and have chosen a surplus above 500 kcal/day. In those cases it shows tailored-advice wording and points you to a GP or registered dietitian.

Is this the same as the calorie deficit calculator?

It runs the same underlying BMR and activity-level calculation, but adds calories instead of subtracting them. Use the calorie deficit calculator to lose weight and this one to gain it.