# Weight Gain Calculator

Calculate your daily calorie surplus for healthy weight gain. Get personalized targets based on your TDEE, goal weight, and timeframe using the Mifflin-St.

## What this calculates

Gaining weight in a healthy, controlled manner requires eating more calories than you burn. This calculator estimates your daily calorie target by computing your TDEE and adding the surplus needed to reach your goal weight within your desired timeframe.

## Inputs

- **Gender**
- **Current Weight** (kg) — min 30, max 300
- **Goal Weight** (kg) — min 30, max 400
- **Height** (cm) — min 100, max 250
- **Age** (years) — min 15, max 120
- **Timeframe** (weeks) — min 1, max 200
- **Activity Level** — options: Sedentary (little or no exercise), Lightly active (1–3 days/week), Moderately active (3–5 days/week), Very active (6–7 days/week), Extra active (very hard exercise/physical job)

## Outputs

- **Estimated TDEE** — Your estimated Total Daily Energy Expenditure
- **Daily Calorie Target** — Calories to eat per day for weight gain
- **Daily Surplus** — Extra calories per day above maintenance
- **Weekly Weight Gain** (kg/week) — Estimated weight gain per week

## Details

Healthy weight gain requires a consistent caloric surplus combined with resistance training to promote lean muscle growth rather than excess fat storage. This calculator uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR), multiplied by your activity factor to determine your Total Daily Energy Expenditure (TDEE). It then calculates the daily caloric surplus needed based on the total weight to gain and your timeframe, using the approximation that 1 kg of body mass requires roughly 7,700 excess calories.

For lean muscle gain, a surplus of 250–500 calories per day (about 0.25–0.5 kg per week) is generally recommended, as larger surpluses tend to produce more fat gain. Protein intake of 1.6–2.2 g per kg of body weight supports muscle protein synthesis. Always consult a healthcare professional or registered dietitian for personalized advice, especially if you are underweight or recovering from illness.

## Frequently Asked Questions

**Q: How much weight can I gain per week safely?**

A: For lean muscle gain, 0.25–0.5 kg (0.5–1 lb) per week is a realistic and healthy target when combined with resistance training. Gaining faster typically results in more fat accumulation. Beginners may gain slightly faster due to "newbie gains."

**Q: Should I eat more protein to gain muscle?**

A: Yes. Research supports consuming 1.6–2.2 grams of protein per kilogram of body weight per day to maximize muscle protein synthesis during a caloric surplus. Distribute protein intake evenly across 3–5 meals throughout the day.

**Q: What if I am gaining mostly fat instead of muscle?**

A: If fat gain is excessive, reduce your surplus to 200–300 calories per day, ensure you are following a progressive resistance training program, eat adequate protein, and prioritize sleep. Without strength training stimulus, most of the surplus will be stored as fat.

**Q: Do I need to track calories every day?**

A: While daily tracking gives the most accurate results, weekly averages are also effective. Focus on hitting your weekly calorie target and weigh yourself under consistent conditions (same time, same scale) to track progress over weeks rather than days.

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Source: https://vastcalc.com/calculators/health/weight-gain
Category: Health & Fitness
Last updated: 2026-04-21