Gaining weight requires eating above your TDEE. This calculator finds your maintenance calories using the Mifflin-St Jeor equation and shows lean, standard, and aggressive surplus targets to help you build muscle with minimal fat gain.
Mifflin-St Jeor equation · Lean & standard bulk targets
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Your gender
Your height
Your weight
Your calorie targets
Maintenance
—
kcal / day
Your calorie baseline — no weight change
Lean Bulk
—
kcal / day
+300 kcal surplus · minimal fat gain
Standard Bulk
—
kcal / day
+500 kcal surplus · faster weight gain
Your BMR—Calories burned at complete rest
Aggressive bulk (+750 kcal)—Fast gain · more fat accumulation
Calculated using the Mifflin-St Jeor equation
These estimates are for informational purposes only and are not medical advice. Consult a registered dietitian or healthcare professional for personalised guidance.
A calorie surplus means eating more calories than your TDEE — giving your body the extra energy needed to build new muscle tissue. Without this surplus, muscle gain is extremely slow even with optimal training.
The size of your surplus determines how fast you gain and how much of that gain is muscle versus fat:
+250–300 kcal/day → Lean bulk: ~0.25 kg/week, mostly muscle
+500 kcal/day → Standard bulk: ~0.45 kg/week, muscle + some fat
+750 kcal/day → Aggressive bulk: ~0.68 kg/week, more fat accumulation
Example — 30-year-old male, 80 kg, moderately active:
TDEE = 2,759 kcal/day
Lean bulk target = 2,759 + 300 = 3,059 kcal/day
Standard bulk = 2,759 + 500 = 3,259 kcal/day
Your Personalised Bulk Targets
How the Mifflin-St Jeor Formula Works
This calculator uses the Mifflin-St Jeor equation — the most validated predictive BMR formula for healthy adults — multiplied by your activity level to give your TDEE.
Eat 300–500 calories above your TDEE. A 300 kcal surplus produces steady lean mass gain with minimal fat. A 500 kcal surplus is faster but adds more body fat alongside muscle. Starting with 300 kcal above maintenance is the most common recommendation for clean weight gain.
How fast should I expect to gain weight? +
With a 300–500 kcal daily surplus and consistent resistance training, most people gain 0.25–0.5 kg per week. Beginners may gain slightly faster. Much faster weight gain typically means excess fat is accumulating alongside any muscle gain.
What foods should I eat to gain weight healthily? +
Focus on calorie-dense whole foods: oats, rice, pasta, sweet potato, nuts, nut butters, olive oil, whole milk, eggs, chicken, red meat, salmon, and legumes. These provide calories alongside protein, carbs, and healthy fats. Avoid relying on processed junk food — the extra calories come with poor nutritional value.
Do I need to lift weights to gain weight healthily? +
Yes. Without resistance training, a calorie surplus causes fat gain rather than muscle gain. Lifting 3–4 times per week ensures most of the surplus calories go toward building muscle rather than being stored as fat. Compound movements like squats, deadlifts, bench press, and rows are the most effective.
How much protein do I need to gain muscle while in a calorie surplus? +
Aim for 1.6–2.2 g of protein per kg of bodyweight per day. At a minimum, hit 1.6 g/kg. Higher protein intakes (up to 2.2 g/kg) may offer additional benefits during a bulk by maximising muscle protein synthesis and limiting fat gain. Spread protein across 3–4 meals for best absorption.