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Health & Fitness

Lean Body Mass Calculator

Estimate lean body mass with the Boer, James or Hume formulas, or from a known body fat percentage.

Your inputs

Results

Lean body mass

56 kg

Lean share of body weight
80%
Implied fat mass
14 kg

≈Estimate based on the stated model and assumptions

Notes for this result

  • This is a population-level estimate for adults, not a diagnosis. Discuss health decisions with a qualified professional.

Inputs are never added to links for financial, salary or health calculators.

What this calculator does

Lean body mass is everything except fat: muscle, bone, organs and water. It is used for some dosing and nutrition calculations.

Formula and method

Boer: men 0.407W + 0.267H − 19.2; women 0.252W + 0.473H − 48.3 From body fat: LBM = W × (1 − BF%)

Worked example

Calculated by this tool with its default inputs:

Inputs

  • Units: Metric (kg, cm)
  • Sex (used by the formula): Male
  • Weight: 70 kg
  • Height: 175 cm
  • Method: Boer (1984)

Results

  • Lean body mass: 56 kg
  • Lean share of body weight: 80%
  • Implied fat mass: 14 kg

How to read the results

Different formulas can differ by a few kilograms; they are population estimates.

Assumptions and limitations

  • An estimate for healthy adults, not a diagnosis or medical advice. Consult a qualified health professional about your personal situation.

Health results are general estimates for adults and do not replace medical advice, diagnosis or treatment. Speak to a qualified health professional about your personal situation, especially during pregnancy or if you have a medical condition.

Questions

Why can the James formula give odd results?

It can become unreliable at high body weights relative to height.

Methodology and verification

Result type
Estimate based on the stated model and assumptions
Formula version
1.0
Automated verification
3 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
Editorial review
Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.

Privacy

Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Because this calculator can involve personal financial or health details, your inputs are never added to share links or saved to history. Privacy policy