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Lean Body Mass Calculator

Enter your sex, weight and height. You get your estimated lean body mass from three published formulas, with their average and the fat mass.

Your numbers

Result

Estimate for information only, not professional advice. Last reviewed .

How we calculate it

Lean body mass is everything in the body except fat. With weight W in kilograms and height H in centimeters, the Boer formula is 0.407 W + 0.267 H − 19.2 for men and 0.252 W + 0.473 H − 48.3 for women. James is 1.1 W − 128 (W ÷ H)² for men and 1.07 W − 148 (W ÷ H)² for women. Hume is 0.3281 W + 0.33929 H − 29.5336 for men and 0.29569 W + 0.41813 H − 43.2933 for women.

For a man of 80 kg and 180 cm they give 61.42, 62.72 and 57.79 kg, an average of 60.64 kg. The fat mass is the weight minus the lean mass, 19.36 kg, which is a body fat estimate of 24.2%.

Assumptions and limits

  • This is an estimate for general information. It is not medical advice and cannot replace a conversation with a doctor.
  • The formulas use only height, weight and sex, so they cannot see how muscular you are. A body scan or skinfold measurement gives a better figure for an individual.
  • They are meant for typical adult body sizes. If a formula gives a result that makes no sense for your height and weight, the calculator says so.

Frequently asked questions

What is lean body mass?

It is your total weight minus your body fat. It includes muscle, bone, organs, skin and the water in them.

Which lean body mass formula is the most accurate?

None of them is exact. They were fitted to groups of people and give different answers for the same person, so the page shows all three and their average.

How is lean body mass different from muscle mass?

Muscle is only part of the lean mass. The rest is bone, organs and water, so lean body mass is always larger than muscle mass.

Related calculators

Worked example (a fixed example using the starting numbers, it does not change as you type)

Inputs: Units = US (pounds, feet and inches); Sex = Male; Weight (pounds) = 176; Height: feet = 5; Height: inches = 11.

  • Lean body mass (average) 133.8 lb
  • Boer 135.5 lb
  • James 138.3 lb
  • Hume 127.5 lb
  • Fat mass (average) 42.2 lb
  • Body fat estimate 24.0 %

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Last reviewed: . Formulas and assumptions are described on our methodology page. For information only; not professional advice.