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Lean Body Mass Calculator
Estimate lean body mass from body-fat percentage or compare Boer and Hume height-and-weight equations in metric or imperial units.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Your measurements
Estimate lean body mass
If measured, this gives the direct estimate: weight × (1 − body-fat fraction).
Estimated lean mass
61.5
kgBased on your entered body-fat percentage
Body-fat method
61.5 kg
Uses your % estimate
Boer (1984)
58.1 kg
Height + weight
Hume (1966)
54.4 kg
Height + weight
Body composition estimate
75.0 kg totalLean mass
61.5 kg
Fat mass
13.5 kg
What lean mass includes
Formula estimates can differ because they were developed from different samples and measurement methods.
How it works
- Select units and the applicable published equation coefficient set.
- Enter height and weight, plus an optional measured body-fat percentage.
- Compare direct, Boer, and Hume estimates while keeping their limitations in mind.
FAQ
Is lean body mass the same as muscle mass?
No. Lean body mass is total body weight minus fat mass, so it also includes water, bones, organs, blood, and other non-fat tissues—not just skeletal muscle.
Which estimate should I use?
A reasonably measured body-fat percentage gives the direct arithmetic estimate. Boer and Hume provide comparisons from height and weight, but all methods have uncertainty and may be less representative outside their original study populations.
Why do the equations ask for a male or female coefficient set?
The historical Boer and Hume publications provide separate sex-based coefficients. The selector chooses that published equation set; it is not a judgment about identity.
Can this be used for medication dosing?
No. This is an educational estimate, not a clinical measurement. Medication or contrast dosing should use the method and supervision specified by a qualified clinician.
Methods shown
| Method | Inputs | Important limitation |
|---|---|---|
| Body-fat method | Weight + body-fat % | Inherits the error of the body-fat measurement |
| Boer (1984) | Height + weight + coefficient set | Regression estimate, not direct measurement |
| Hume (1966) | Height + weight + coefficient set | Developed from a small historical sample |
Equation context: Boer, American Journal of Physiology (1984); Hume, Journal of Clinical Pathology (1966).