Calculate your lean body mass and fat mass from weight and height (Boer formula) or from your body fat percentage. Enter your values; the result updates as you type, with the method shown below.
About this calculator
Lean body mass is everything in your body except fat: muscles, bones, organs and water. It is useful for setting protein targets, dosing some medicines and following body composition beyond the scale.
Enter your sex, weight and height, and your body fat percentage if you know it. The calculator shows your lean mass and fat mass, with the Boer formula or from your body fat.
When to use it
- Setting protein intake per kg of lean mass.
- Following a training programme.
- Complementing BMI.
- Understanding body composition results.
How to read the result
Lean mass = weight × (1 − body fat %). Without a body fat figure, the Boer formula estimates it from weight and height.
A measured body fat percentage gives a more precise result.
Mistakes to avoid
- Comparing results from different methods.
- Expecting lean mass to be only muscle.
- Measuring at different times of day.
Formula
Boer: men 0.407W + 0.267H − 19.2; women 0.252W + 0.473H − 48.3
Worked example
Man, 80 kg, 178 cm: lean mass about 60.9 kg.
Frequently asked questions
What is lean body mass?
Everything except fat: muscles, bones, organs and water.
Which is more precise?
Entering a measured body fat % gives a better result.
Is lean mass the same as muscle?
No, it also includes bones, organs and water.
How do I know my body fat?
With our body fat calculator, a smart scale or a DEXA scan.
Why does it matter?
It shows changes the scale alone hides.
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Results are estimates for information only. Check important figures with a professional.