# Weight Gain Calculator

URL: https://speedycalculator.com/calculators/health/weight-gain/
Last updated: 2026-10-30

> The weight gain calculator works out how many calories to eat each day to reach a goal weight by a chosen weekly rate, how long it will take and how much protein supports muscle rather than fat gain.

## Inputs

- Sex
- Age (years)
- Weight (kg, lb, st, g)
- Height (cm, in, m, ft, mm)
- Activity level
- Goal weight (kg, lb, st, g)
- Weekly weight gain (kg, lb, st, g)

## Results

- Maintenance calories
- Daily calories to gain weight
- Daily surplus
- Time to reach your goal
- Protein to support muscle (1.6 g/kg)

## Formula

```
Daily surplus = weekly gain × 7,700 kcal/kg ÷ 7
Intake = TDEE + surplus
Weeks = (goal − current) ÷ weekly gain
```

## Explanation

Gaining weight slowly, at about 0.25–0.5 kg (0.5–1 lb) a week, with resistance training and enough protein, helps more of the gain be muscle. Faster gains are mostly fat.

### How to use the Weight Gain Calculator

- **Sex**
- **Age**
- **Weight**
- **Height**
- **Activity level**
- **Goal weight**
- **Weekly weight gain**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter your details, activity level, goal weight and weekly gain. The calculator finds your TDEE with Mifflin–St Jeor, adds the surplus and divides the total gain by your weekly rate.

### Inputs explained

FieldWhat to enterSexChoose one: Male, FemaleAgeIn yearsWeightUnits: kg, lb, st, gHeightUnits: cm, in, m, ft, mmActivity levelChoose one: Basal metabolic rate (no activity), Sedentary – little or no exercise, Light – exercise 1–3 times a week, Moderate – exercise 4–5 times a week …Goal weightUnits: kg, lb, st, gWeekly weight gainUnits: kg, lb, st, g

### What each result means

- **Daily calories to gain weight** = [Maintenance calories] + [Weekly weight gain]×7700÷7
- **Daily surplus** = [Weekly weight gain]×7700÷7
- **Time to reach your goal** = ([Goal weight] - [Weight])÷[Weekly weight gain]
- **Protein to support muscle (1.6 g/kg)** = 1.6×[Weight]

### Example values

How the main result changes when **Age** changes and everything else stays at the example values above:

Age (years)Daily calories to gain weight (kcal/day)152,90122.52,846302,79137.52,736452,681602,571
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Sex: Male; Age: 30 years; Weight: 75 kg; Height: 178 cm; Activity level: Moderate – exercise 4–5 times a week; Goal weight: 82 kg; Weekly weight gain: 0.25 kg.

Results — Maintenance calories = 2,516 kcal/day; **Daily calories to gain weight = 2,791 kcal/day**; Daily surplus = 275 kcal/day; Time to reach your goal = 28 weeks; Protein to support muscle (1.6 g/kg) = 120 g/day.

## Key terms

- **Calorie surplus**: Eating more calories than you burn.

## FAQ

**How fast should I gain weight?**
About 0.25–0.5 kg (0.5–1 lb) a week for lean gains.

**What should I eat?**
Energy-dense whole foods: nuts, dairy, whole grains, olive oil, eggs, meat or legumes.

**Why am I not gaining?**
Your activity may be higher than you think; add 200–300 kcal and reassess.


## Sources

- [Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr, 1990](https://pubmed.ncbi.nlm.nih.gov/2305711/)
- [Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. Am J Clin Nutr, 1984](https://pubmed.ncbi.nlm.nih.gov/6741850/)
- McArdle WD, Katch FI, Katch VL. Exercise Physiology: Nutrition, Energy and Human Performance