How the Weight Gain Calculator works
Uses the same 7,700 kcal/kg principle as the weight loss calculator, applied in reverse. To gain 1 kg, you need a cumulative surplus of approximately 7,700 kcal.
Daily calories = TDEE + calorie surplus
Weeks to goal = (kg to gain × 7,700) ÷ daily surplus ÷ 7
Weeks to goal = (kg to gain × 7,700) ÷ daily surplus ÷ 7
Choosing your surplus
| Surplus | Gain/week | Best for |
|---|---|---|
| 250 kcal | ~0.23 kg/week | Lean bulk — minimises fat gain |
| 500 kcal | ~0.45 kg/week | Standard bulk — balanced approach |
| 750 kcal | ~0.68 kg/week | Aggressive — more fat gain risk |
How to use your results
Hit your daily calorie target consistently and train progressively. Without resistance training, most of the weight gained will be fat rather than muscle.
Protein is critical for muscle gain — aim for 1.8–2.2g per kg of body weight. Distribute protein across 3–4 meals of 30–40g each for optimal muscle protein synthesis.
Track your weight weekly (morning, same conditions). If gaining less than target rate for 2+ weeks, increase calories by 100–150 kcal. If gaining faster than desired, reduce by the same amount.
Frequently asked questions
How many calories do I need to gain weight?
You need to eat more than your TDEE (maintenance calories). A 250–500 kcal daily surplus produces 0.25–0.5 kg of weight gain per week. Use the TDEE calculator to find your maintenance, then add your desired surplus.
How fast can I gain muscle naturally?
Natural muscle gain is approximately 0.5–1 kg per month for beginners, 0.25–0.5 kg for intermediate lifters. Most weight gained beyond these rates will be fat, not muscle. A lean bulk with small surplus is optimal for muscle gain.
What is a lean bulk?
A lean bulk uses a small calorie surplus (200–300 kcal/day) to gain muscle while minimising fat accumulation. It's slower than a traditional bulk but results in better body composition. Recommended for those who want to gain muscle without significant fat gain.
How much protein should I eat to gain muscle?
1.6–2.2g of protein per kg of body weight per day. For a 75kg person, that's 120–165g protein daily. Distribute across 3–4 meals (30–40g per meal) to maximise muscle protein synthesis.
Should I use a weight gainer supplement?
Only if you genuinely cannot eat enough whole food calories. Most weight gainers are expensive and provide little more than carbs and protein. Whole foods (oats, rice, potatoes, meat, eggs, nuts) are more nutritious and usually cheaper.
Is it possible to gain muscle and lose fat simultaneously?
Yes — body recomposition is possible for beginners, those returning after a break, and people with higher body fat. It requires eating at maintenance, high protein (2.0g/kg), and consistent resistance training.
How do I know if I'm gaining muscle or just fat?
Track body measurements (waist, chest, arms) alongside weight. If waist is growing proportionally to everything else, fat gain may be dominant. Strength increases in the gym are the best indicator of muscle gain.
What foods are best for weight gain?
Calorie-dense whole foods: oats (370 kcal/100g), rice (130 kcal cooked), pasta, sweet potato, eggs, chicken, salmon, Greek yogurt, nuts (550–650 kcal/100g), avocado (160 kcal/100g), olive oil (884 kcal/100ml), and nut butters.