💪 Lean Body Mass Calculator
Enter your sex, height and weight to estimate lean body mass (everything except fat) using the Boer and James formulas, with an estimated fat mass and percentage.
Quick answer: Boer formula for men: LBM = 0.407 × weight(kg) + 0.267 × height(cm) − 19.2. A man of 70 kg and 175 cm has a lean body mass of 56.0 kg.
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Lean Body Mass Calculator inputs
Result
Lean body mass (Boer)
56 kg
Estimated body fat: 20%
| Boer formula | 56 kg |
| James formula | 56.5 kg |
| Average of both | 56.3 kg |
- Estimated fat mass
- 14 kg
For general information only – not medical advice. Consult a healthcare professional.
How lean body mass is calculated
These equations estimate lean mass from sex, height and weight. This calculator shows the Boer formula (1984) and the James formula (1976).
Boer (men) = 0.407 × W + 0.267 × H − 19.2 · Boer (women) = 0.252 × W + 0.473 × H − 48.3
W is weight in kg and H is height in cm. The James formula is men: 1.1 × W − 128 × (W/H)² and women: 1.07 × W − 148 × (W/H)².
Example: a man of 70 kg and 175 cm: 0.407 × 70 + 0.267 × 175 − 19.2 = 56.0 kg lean mass. Fat mass is 70 − 56.0 = 14.0 kg, about 20%. James gives 56.5 kg.
Typical lean mass share
| Group | Typical body fat |
|---|---|
| Athletic men | 6–17% |
| Average men | 18–24% |
| Athletic women | 14–24% |
| Average women | 25–31% |
Notes
- These are estimates, so use them to track trends rather than as exact values.
- Very muscular or very overweight people may see larger errors.
- Combine with waist and body fat measurements for context.
For general information only – not medical advice.
Frequently asked questions
What is lean body mass?
It is your total body weight minus fat: muscle, bone, organs, skin and body water. It is also called fat-free mass.
Which formula is more accurate?
Boer and James are both widely used estimates and usually agree within a few kilograms. For accuracy, DEXA scans or bioimpedance devices are better.
Why does lean body mass matter?
It drives your resting metabolism, is used to dose some medicines, and tracking it helps you see whether weight change is muscle or fat.
How can I increase lean body mass?
Strength training, enough protein and sleep, and a modest calorie surplus support muscle gain. Consult a professional before major diet changes.
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