Lean Body Mass Calculator
Calculate lean body mass using the Boer, James or Hume formulas.
Tip: LBM is used in medicine for dosing anaesthetics and chemotherapy drugs — it is more accurate than total weight for these purposes.
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About this digital tool
The lean body mass (LBM) calculator works out the weight of your body without fat: muscles, bones, organs and water. Enter your weight, height and gender and get the result with three formulas: Boer, James and Hume, plus their average and an estimate of the fat percentage.
The formulas are regressions that link weight and height to lean mass, with different coefficients for men and women. The fat percentage is simply the remaining part of total weight. They are estimates for the general population, not measurements; athletes with lots of muscle or people with a lot of fat may deviate from the average. For accurate measurement use DEXA or bioimpedance. For drug doses or medical decisions, don't rely on this tool.
How to use
- Enter your current weight (kg)
- Enter your height (cm)
- Choose your gender
- See LBM by the 3 formulas
- See the estimated body fat percentage
Frequently asked questions
What is lean body mass?
LBM = Total weight - Fat mass. It includes muscles, bones, organs, body water. For men it averages 75–85% of weight, for women 65–75%.
Why is it important?
LBM shows how much functional mass you have. Two people of the same weight can have very different LBM — the one with a higher LBM has more muscle and a faster metabolism.
Which formula is the most accurate?
The Boer formula (1984) is considered the most accurate for most of the population. James (1976) is more conservative, Hume (1966) gives slightly higher values. The average of the three formulas gives the best estimate.
Which LBM formula is more accurate?
Boer, James and Hume give similar results for average people. The average of the three is a reasonable estimate; none replaces measurements such as DEXA.