Body Recomposition Calculator
Estimate the daily calorie target needed to simultaneously lose fat and gain muscle based on lean body mass, training frequency, experience, and your recomposition focus. Best used by natural lifters aiming to change body composition without a strict bulk or cut.
Last updated: September 2026
Formula below · 3 sources (acsm.org, nsca.com, Wikipedia) · Updated Sep 2026
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About this calculator
Body recomposition — losing fat while gaining muscle concurrently — is most achievable in beginners, people returning after a layoff, and those with higher body fat percentages. The calorie target is anchored to lean body mass (LBM) with the Katch-McArdle equation: LBM_kg = weight_lb × 0.453592 × (1 − body_fat% / 100); BMR = 370 + 21.6 × LBM_kg. Maintenance (TDEE) is BMR × an activity factor from your training days: 1.2 + 0.0875 × days, which gives the standard 1.375 at 2 days, 1.55 at 4 days and 1.725 at 6 days a week. Finally, a goal adjustment is made: −300 kcal for fat-loss focus, −100 kcal for balanced recomp, or +100 kcal for muscle-gain focus. The full formula: calories = round((370 + 21.6 × LBM_kg) × (1.2 + 0.0875 × training_days) + goal_adjustment). Keep protein high (about 0.8–1.0 g per lb) and adjust by 100 kcal if your weight trend over 2–3 weeks moves faster than intended.
How to use
Example: 200 lb person, 25% body fat, trains 4 days/week, balanced recomp goal. LBM = 200 × 0.453592 × 0.75 = 68.04 kg. BMR = 370 + 21.6 × 68.04 = 1,839.6 kcal. Activity factor = 1.2 + 0.0875 × 4 = 1.55, so maintenance ≈ 2,851.4 kcal. Balanced adjustment: 2,851.4 − 100 ≈ 2,751 kcal/day. Fat-loss focus gives about 2,551 kcal and muscle focus about 2,951 kcal.
Frequently asked questions
Is it really possible to lose fat and build muscle at the same time?
Yes, but the degree to which it is possible depends heavily on training experience and initial body composition. Beginners and those returning from a break can achieve significant recomposition because their muscles are highly responsive to resistance training and their bodies can partition nutrients efficiently even in a slight deficit. Advanced, already-lean lifters find true recomposition very slow and may achieve better long-term results by alternating structured bulking and cutting phases. Higher body fat levels also create a metabolic environment more conducive to simultaneous fat loss and muscle gain.
How should I set my calories for a body recomposition diet?
Unlike a strict cut or bulk, recomposition typically targets a very small caloric adjustment — around maintenance or slightly below. Eating too aggressively in a deficit compromises muscle protein synthesis and recovery, while a large surplus accelerates fat gain. A common recommendation is to stay within 100–300 kcal below maintenance, ensure high protein intake (0.8–1.0 g/lb), and time carbohydrates around training sessions. This calculator accounts for lean body mass and training frequency to personalise that maintenance estimate before applying your chosen goal adjustment.
Why does the calculator use lean body mass instead of total weight?
Resting energy use comes mostly from lean tissue, so the Katch-McArdle equation (BMR = 370 + 21.6 × lean mass in kg) is more accurate than weight-based equations for people whose body fat is well above or below average. Two people who both weigh 200 lb burn different amounts at rest if one carries 15% fat and the other 30%. Training experience is not an input: it changes how fast you can recomp, not how many calories you burn.