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Lean Body Mass Calculator

Estimate lean body mass with a formula method and, when available, a body-fat-percentage method.

Formula estimates are population approximations. If you have a reliable body-fat measurement, the body-fat method is often easier to interpret.

Method

The formula estimate uses the Boer equation. The optional body-fat method calculates lean mass as body weight multiplied by one minus body fat percentage.

Example

If body weight is 75 kg and body fat is 22%, the body-fat method estimates lean body mass as 75 x 0.78 = 58.5 kg.

Common mistakes

Do not treat a formula estimate as a scan result. If you enter body fat percentage, make sure it came from a method you trust.

Limitations

This is not a clinical body-composition test. Formula estimates can be inaccurate for athletes, older adults, children, pregnancy or medical conditions.

References

Last reviewed: 2026-05-17

Before relying on this result

Use this calculator together with the formula, assumptions, limitations and examples on the page. If the topic involves health, tax, lending, investment, legal, safety or current-rate decisions, treat the number as an estimate and check the relevant primary source or professional guidance.

Calculator metadata last reviewed: 2026-05-14.