About this calculator
Enter your height, weight and sex. The Boer formula is the most commonly used; James and Hume are shown for comparison.
How to use it
- Choose your sex.
- Enter height and weight.
- Compare the three estimates.
The formula
Boer: men 0.407 W + 0.267 H − 19.2; women 0.252 W + 0.473 H − 48.3
- W
- weight in kg
- H
- height in cm
Worked example
A man 170 cm, 68 kg
- Boer = 0.407 × 68 + 0.267 × 170 − 19.2 = 53.9 kg.
- James gives 54.3 kg and Hume 50.5 kg.
- So roughly 21% of body weight is fat.
What the result means
If you know your body fat percentage, weight × (1 − body fat) is a better estimate.
Assumptions
- Adult of average build.
Limitations
- Formulas assume average body composition; athletes and people with obesity can differ a lot.
Frequently asked questions
What is a normal lean body mass?
Commonly about 75% to 85% of body weight in men and 65% to 75% in women.
Which formula is best?
Boer is the most widely used for adults; all three are estimates.
How do I increase lean mass?
Strength training with enough protein and calories.
Not medical advice. This calculator is a general screening tool and cannot diagnose any condition. Results are estimates. Please talk to a doctor or a qualified health professional about your health and before making changes to diet, exercise or treatment.
Last reviewed on 1 October 2026. Found a mistake? Tell us.