Body Recomposition Calculator Formula

Understand the math behind the body recomposition calculator. Each variable explained with a worked example.

Use the Body Recomposition Calculator

Formulas Used

Target Calories

recomp_calories = round(tdee * 0.95)

Protein Target

protein_g = round(lean_mass * 0.453592 * 2.2)

Lean Body Mass

lean_mass_display = round(lean_mass)

Fat Mass

fat_mass = round(body_weight * body_fat_pct / 100)

Variables

VariableDescriptionDefault
body_weightBody Weight(lbs)180
body_fat_pctBody Fat %(%)20
activity_levelActivity Level1.55
lean_massDerived value= body_weight * (1 - body_fat_pct / 100)calculated
bmrDerived value= 10 * lean_mass * 0.453592 + 6.25 * 178 - 5 * 30 + 5calculated
tdeeDerived value= bmr * activity_levelcalculated

How It Works

How Body Recomposition Works

Body recomposition means losing fat while building muscle simultaneously, typically at or slightly below maintenance calories.

Formula

Recomp Calories = TDEE x 0.95 (slight deficit of 5%)

Protein = Lean Mass (kg) x 2.2 g/kg

Key Principles

  • Eat at or just below maintenance calories
  • Prioritize high protein intake (1g per lb of lean mass)
  • Lift heavy with progressive overload
  • Get adequate sleep (7-9 hours)

    • Recomp works best for beginners, those returning from a break, or those with higher body fat.

    Worked Example

    A 180 lb person at 20% body fat with moderate exercise.

    body_weight = 180body_fat_pct = 20activity_level = 1.55
    1. 01Lean mass = 180 * 0.80 = 144 lbs = 65.3 kg
    2. 02BMR estimate = 10 * 65.3 + 6.25 * 178 - 5 * 30 + 5 = 1,621 kcal
    3. 03TDEE = 1,621 * 1.55 = 2,513 kcal
    4. 04Recomp calories = 2,513 * 0.95 = 2,387 kcal/day
    5. 05Protein = 65.3 * 2.2 = 144 g/day

    Ready to run the numbers?

    Open Body Recomposition Calculator