Lean Body Mass Calculator
Lean Body Mass: 127.5 lb
- Boer (1)
- 127.5 lb · 20% body fat
- James (2)
- 129.0 lb · 19% body fat
- Hume (3)
- 120.4 lb · 25% body fat
What this lean body mass calculator does
Lean body mass is the part of your weight that is not fat: muscle, bone, organs, and water. This calculator estimates it with three adult formulas — Boer, James, and Hume — and converts each estimate into a body fat percentage.
The formulas use height, weight, and sex. They are estimates from population data, not a scan of your body.
How to use this calculator
- Choose US or metric units.
- Select sex.
- Enter height and weight.
- Click Calculate to see lean mass and body fat percentage for each formula.
The default example is a man who is 5 ft 10 in tall and weighs 160 lb.
Lean body mass formulas
Boer:
men: 0.407 × weight(kg) + 0.267 × height(cm) − 19.2
women: 0.252 × weight(kg) + 0.473 × height(cm) − 48.3
James:
men: 1.1 × weight − 128 × (weight / height)²
women: 1.07 × weight − 148 × (weight / height)²
Hume:
men: 0.32810 × weight + 0.33929 × height − 29.5336
women: 0.29569 × weight + 0.41813 × height − 43.2933
Weight is in kilograms and height is in centimeters. Body fat percentage is (weight − lean mass) ÷ weight × 100.
What the results mean
For the default example, the three formulas estimate 127.5 lb, 129.0 lb, and 120.4 lb of lean mass, with body fat estimates of 20%, 19%, and 25%.
A higher lean mass estimate means a lower body fat estimate for the same weight. The differences between formulas are expected; they were built from different populations and measurement methods.
Assumptions and limitations
The formulas are for adults. They do not include the age-14-or-younger formulas used by some calculators, and they do not account for pregnancy, very high muscle mass, amputation, or medical conditions. They are not a DEXA scan, hydrostatic weighing, or air displacement measurement.
Use the range across formulas rather than treating one number as exact. If you need clinical body composition, use a validated measurement method.
Frequently asked questions
Why do the formulas disagree?
They were derived from different study populations and use different combinations of height, weight, and sex. A spread of several pounds is normal.
Which formula should I use?
There is no single best formula. Boer is a common general estimate; James and Hume are alternatives. Look at the range and track changes over time with the same method.
Does lean body mass include water and bone?
Yes. Lean mass includes muscle, bone, organs, and body water. It is not the same as muscle mass alone.
Can I use this for children?
No. These are adult formulas. Children and teenagers need age- and sex-specific methods.
Reference table
Lean body mass formulas
| Formula | Lean Body Mass | Body Fat |
|---|---|---|
| Boer | Men: 0.407 × weight + 0.267 × height − 19.2. Women: 0.252 × weight + 0.473 × height − 48.3 | Weight − lean mass |
| James | Men: 1.1 × weight − 128 × (weight ÷ height)². Women: 1.07 × weight − 148 × (weight ÷ height)² | Weight − lean mass |
| Hume | Men: 0.32810 × weight + 0.33929 × height − 29.5336. Women: 0.29569 × weight + 0.41813 × height − 43.2933 | Weight − lean mass |
Weight is in kilograms and height in centimeters. These equations are estimates; body composition devices and individual variation affect accuracy.
Source
References:
Disclaimer
This calculator is for informational and educational purposes only. It is not a medical diagnosis or a substitute for clinical body composition testing. Consult a qualified health professional for personalized advice.