Lean Body Mass Calculator: Boer, James and Hume Formulas
Enter sex, height and weight to estimate how much of your weight is lean mass: muscle, bone, organs and water.
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Lean body mass (Boer)
54.7kg
- James formula
- 55.3 kg
- Hume formula
- 51.1 kg
- Implied body fat
- 21.9%
An estimate for general information, not medical advice.
Estimates from height and weight only. A tape or scan measurement of body fat is more personal.
How to use
- Choose male or female.
- Enter height and weight.
- Compare the three formulas and the implied body fat.
Good to know
Boer (1984): men 0.407W + 0.267H − 19.2; women 0.252W + 0.473H − 48.3. James (1976): men 1.1W − 128(W/H)²; women 1.07W − 148(W/H)². Hume (1966): men 0.32810W + 0.33929H − 29.5336; women 0.29569W + 0.41813H − 43.2933. W in kg, H in cm.
Boer is shown first because it holds up best across body sizes. The James formula is known to give falling, unrealistic values at high body weight, so ignore it if it looks too low.
These are population estimates from height and weight only. If you know your body fat %, lean mass = weight × (1 − fat %) is more personal. Used by the Katch-McArdle BMR formula and for protein planning.
Questions
What is lean body mass?
Everything in your body that is not fat: muscle, bone, organs, skin and water. It is usually 70–85% of weight in men and 60–75% in women.
Which formula should I trust?
Boer is the most used today. When the three disagree a lot, your build is far from average and a body fat measurement will help.
Is lean body mass the same as muscle?
No. Muscle is only part of it, usually about half.
How can I increase lean mass?
Strength training 2–3 times a week and enough protein are the proven basics. Gains are slow, about 0.5–1 kg a month at best for beginners.
Is my data stored?
No. Everything is calculated on your device.