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Lean Body Mass Calculator

Lean body mass (fat-free mass) by the Boer, James and Hume formulas, or from a known body-fat percentage.

Enter values

Results update as you type.

Result

Lean body mass (Boer)

60.9 kg

James formula
62.1 kg
Hume formula
57.1 kg
Body fat mass (Boer)
19.1 kg

Educational estimate only — not medical advice. Talk to a healthcare professional about your individual situation.

About the Lean Body Mass Calculator

Lean body mass (fat-free mass) by the Boer, James and Hume formulas, or from a known body-fat percentage.

Also known as: lbm calculator, fat free mass, ffm calculator, muscle mass estimate, fat-free-mass.

How to use this calculator

  1. Enter units, sex, known body fat % (optional) and the other fields.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

Boer (male): 0.407·kg + 0.267·cm − 19.2

Worked example

Using the values pre-filled in the calculator above:

  • Units: Metric (kg, cm)
  • Weight = 80 kg
  • Height = 178 cm
  • Sex: Male
  • Known body fat % (optional) = 0 %

the calculator returns:

  • Lean body mass (Boer): 60.9 kg
  • James formula: 62.1 kg
  • Hume formula: 57.1 kg
  • Body fat mass (Boer): 19.1 kg