Lean Body Mass Calculator – Boer, James & Hume Formulas
Lean Body Mass Estimates
| Formula | LBM | Body Fat % |
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Average Lean Body Mass
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Average Body Fat %
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Understanding Lean Body Mass
Lean Body Mass (LBM) is your total body weight minus your body fat. It includes muscle, bone, organs, water, and everything that isn't fat tissue. Knowing your LBM helps you set realistic fitness goals, calculate accurate protein needs, and monitor whether you are gaining muscle or losing fat during training.
This calculator uses three well-established prediction formulas. The Boer formula (1984) is considered one of the most accurate for general populations. The James formula (1976) was one of the earliest published LBM equations. The Hume formula (1966) uses similar regression analysis. All three use only height and weight as inputs, making them convenient though less precise than methods like DEXA scans or hydrostatic weighing.
Results from different formulas may vary by a few kilograms, which is normal. The average of all three gives a reasonable estimate. For tracking progress over time, consistency matters more than absolute accuracy — use the same formula and measurement conditions each time. These formulas work best for average-build adults and may be less accurate for very muscular individuals or those with extreme body compositions.
Frequently Asked Questions
What is lean body mass?
Lean Body Mass (LBM) is your total body weight minus all fat tissue. It includes muscle, bone, organs, skin, blood, and water. LBM is useful for calculating protein requirements and tracking body composition changes.
How accurate are the Boer, James, and Hume formulas?
These formulas provide estimates based on statistical regression from population studies. They are reasonably accurate for average-build adults but may have errors of 2-5 kg. For precise measurements, DEXA scanning or hydrostatic weighing are recommended.
What is a normal body fat percentage?
For men, a healthy athletic range is 6-17%. For women, a healthy athletic range is 14-24%. Average ranges are 18-24% for men and 25-31% for women. These vary by age.
How can I increase my lean body mass?
Build muscle through progressive resistance training combined with adequate protein intake (1.6-2.2 g per kg of body weight per day). Sufficient sleep, caloric surplus during bulking phases, and consistent training are the key factors.