Calculate your fat-free body weight with clinical precision.
In the world of professional fitness and clinical nutrition, your total body weight is only half the story. Whether you are a competitive bodybuilder in Los Angeles, a marathon runner in London, or a health-conscious individual in Sydney, understanding your Lean Body Mass (LBM) is vital. Lean Body Mass represents everything in your body—muscles, bones, organs, and water—excluding body fat. An Lean Body Mass Calculator is the most effective way to track true muscle growth and ensure your weight loss journey targets fat, not vital tissue.
Our online LBM solver utilizes the most accurate physiological formulas, including the Boer, James, and Hume equations. By calculating your fat-free mass, you can accurately determine your protein requirements, optimize your metabolic rate, and tailor your training program for peak physical performance.
Understanding your Lean Body Mass helps explain three important aspects of your health:
Muscle tissue is metabolically active, meaning it burns more calories at rest than fat tissue. The higher your Lean Body Mass, the higher your resting metabolism tends to be.
Some sports nutrition guidance uses LBM rather than total body weight to estimate protein needs, since lean tissue — not fat — is what primarily requires dietary protein to maintain and build.
If the scale doesn't move but your LBM increases relative to your fat mass, you may be simultaneously losing fat and gaining muscle — a process often called body recomposition.
This calculator specifically uses the Boer Formula (1984), one of the most widely referenced equations for estimating lean body mass from height and weight alone.
Boer — Men: LBM = (0.407 × weight in kg) + (0.267 × height in cm) − 19.2
Boer — Women: LBM = (0.252 × weight in kg) + (0.473 × height in cm) − 48.3
Other formulas exist — such as the James Formula and the Hume Formula — which sometimes give slightly different results. This calculator uses Boer specifically, which is well-regarded for general fitness assessments.
| Profile | Estimated LBM | Body Fat | Lean % |
|---|---|---|---|
| Male, 70 kg, 175 cm | 56.0 kg | 14.0 kg | 80% |
| Female, 60 kg, 165 cm | 44.9 kg | 15.1 kg | 75% |
| Male, 85 kg, 180 cm | 63.5 kg | 21.5 kg | 75% |
| Female, 65 kg, 160 cm | 43.8 kg | 21.2 kg | 67% |
Values calculated directly using this calculator's Boer formula.
| Classification | Men (Avg LBM %) | Women (Avg LBM %) |
|---|---|---|
| Athlete | 86% – 94% | 79% – 86% |
| Fitness | 82% – 85% | 75% – 78% |
| Average | 75% – 81% | 69% – 74% |
| Obese | < 75% | < 68% |
Lean Body Mass gives you a fuller picture of your physique than total weight alone, helping you distinguish real muscle changes from simple water fluctuations. Use the calculator above periodically to track trends over time, and pair it with resistance training and adequate protein intake to support a healthy lean mass.