Weight Gain Calculator
Find out how many calories to eat each day to gain weight at the pace you choose, the macro split for a lean or standard bulk, and the date you can expect to reach your target.
Last updated:
Lean bulk 0.25–0.5 lb; standard 0.5–1 lb
Lean bulk 0.1–0.25 kg; standard 0.25–0.5 kg
How to use the Weight Gain Calculator
- Choose units and enter your sex, age, height and activity level.
- Enter your current and target weight.
- Set a weekly gain rate, or use the Lean bulk and Standard bulk presets.
- Read your daily calories and macros.
- Follow the weekly plan and re-weigh yourself to adjust.
How the weight gain plan is calculated
- BMR with the Mifflin-St Jeor equation: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men or − 161 for women.
- Maintenance calories (TDEE) = BMR × activity factor (1.2 sedentary to 1.9 very active).
- Daily surplus = weekly gain (kg) × 7,700 kcal ÷ 7. In pounds: weekly gain (lb) × 3,500 ÷ 7.
- Intake = maintenance + surplus.
- Macros: protein from g/kg of body weight, fat at 25% of calories, carbohydrate fills the rest.
- Goal date = today + (target − current) ÷ weekly rate.
Choosing a gain rate
| Approach | Weekly gain | Daily surplus | Best for |
|---|---|---|---|
| Slow / lean bulk | 0.1–0.25 kg (0.25–0.5 lb) | ~110–275 kcal | Experienced lifters, minimizing fat gain |
| Standard bulk | 0.25–0.5 kg (0.5–1 lb) | ~275–550 kcal | Beginners and intermediates |
| Fast gain | 0.5–0.75 kg (1–1.5 lb) | ~550–825 kcal | Underweight people under medical guidance, very lean hard gainers |
Tips for gaining weight well
- Lift weights or do resistance training 3–4 times a week so the extra calories build muscle.
- Weigh yourself at the same time several mornings a week and use the weekly average; daily weight swings by 1–2 lb from water.
- If the average does not move for two weeks, add 100–200 kcal a day. If you gain much faster than planned, cut back by the same amount.
- Spread protein over 3–5 meals of roughly 0.3–0.4 g/kg each.
- Unexplained weight loss or difficulty gaining weight despite eating more is worth discussing with a doctor.
Frequently asked questions
How many calories do I need to gain weight?
Eat more than your maintenance calories (TDEE). Using the common estimate of about 7,700 kcal per kilogram (3,500 kcal per pound), gaining 0.25 kg a week needs a surplus of about 275 kcal a day and 0.5 kg a week about 550 kcal a day.
How fast should I gain weight when bulking?
A common guideline is about 0.25 to 0.5 percent of body weight per week for a lean bulk, and up to about 1 percent for beginners. Faster gain mostly adds fat rather than muscle.
How much protein do I need to build muscle?
Research on resistance training suggests about 1.6 g of protein per kg of body weight per day captures most of the benefit, with up to about 2.2 g/kg used by many athletes. That is 0.7 to 1 g per pound.
Why does my calorie target increase over time?
A heavier body burns more energy, so your maintenance calories rise as you gain. The weekly plan recalculates maintenance from your projected weight each week and adds the same surplus, so your rate of gain stays on track.
Is the 3,500 calories per pound rule accurate?
It is a useful approximation for fat tissue. Muscle contains more water and takes fewer stored calories per pound, but building it also costs energy, and individual responses vary. Weigh yourself regularly and adjust intake by 100 to 200 kcal if you gain faster or slower than planned.
What are healthy ways to eat more calories?
Add an extra meal or snack, choose energy-dense foods such as nuts, nut butters, olive oil, whole milk, yogurt, oats, rice, potatoes, eggs and dried fruit, and drink smoothies. Combine the extra food with strength training so more of the gain is muscle.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.