Your lean body mass, from three research formulas.
Enter your weight, height, sex and body fat percentage and see your estimated lean body mass instantly. The headline uses the Boer formula, with James and Hume estimates plus your own body fat percentage shown side by side so you can compare methods.
Your details
Lean body mass formulas differ by sex.
Your total height in inches (used by all three formulas).
Your total body weight in pounds.
Your estimated body fat percentage.
The Boer, James and Hume formulas estimate lean body mass from weight, height and sex alone. If you also know your body fat percentage, the calculator shows the direct estimate (weight minus fat mass) alongside the formulas. Results update as you type.
What your lean body mass means
How the three formulas compare
Lean mass share milestones at your weight
Estimates by method
Each method estimates lean body mass slightly differently. The highlighted row is the Boer formula, used for the headline result.
| Method | Lean body mass | Fat mass | LBM % of weight | Notes |
|---|
Lean body mass, explained
What is Lean Body Mass?
Lean body mass (LBM) is your total weight minus your fat mass. It includes muscle, bone, organs, water, and connective tissue, essentially everything in your body that is not fat. Tracking LBM helps you distinguish between healthy weight gain (muscle) and unhealthy weight gain (fat).
Why Lean Body Mass Matters
LBM is a better indicator of fitness and health than total weight alone. Two people can weigh the same but have very different body compositions. Higher lean body mass is associated with a faster metabolism, better insulin sensitivity, greater strength, and improved overall health outcomes.
How to Increase Lean Body Mass
Building lean body mass requires progressive resistance training combined with adequate protein intake (0.7-1g per pound of body weight) and a slight caloric surplus. Compound exercises like squats, deadlifts, bench press, and rows are the most effective. Consistency and progressive overload over months and years yield the best results.
Tracking Body Composition Changes
Monitor your body composition every 4-6 weeks rather than daily. Use consistent measurement methods such as calipers, bioelectrical impedance scales, or DEXA scans. Take measurements at the same time of day under similar conditions. Track trends over time rather than focusing on individual readings.
Common questions
What is a good lean body mass?
Lean body mass varies by individual. Generally, men carry more lean mass than women. For men, LBM is typically 75-85% of total weight, and for women, 65-75%. Athletes and bodybuilders may have LBM above 85% of total weight.
Can I gain muscle and lose fat at the same time?
Yes, body recomposition is possible, especially for beginners, those returning to training after a break, and overweight individuals. It requires adequate protein, resistance training, and eating near maintenance calories. The process is slower than dedicated bulking or cutting phases.
How do I measure my body fat percentage?
Common methods include skinfold calipers, bioelectrical impedance scales, the US Navy tape method, DEXA scans, and hydrostatic weighing. DEXA scans are the gold standard for accuracy. For tracking trends, consistency of method matters more than absolute accuracy.
Does lean body mass affect metabolism?
Yes, lean body mass is the primary determinant of your resting metabolic rate. Each pound of muscle burns approximately 6-7 calories per day at rest, while each pound of fat burns only about 2 calories. This is why building muscle helps with long-term weight management.
This calculator gives a formula-based estimate, not a medical measurement. The Boer, James and Hume equations were derived from population averages and can be off by several pounds for very lean, very muscular or very obese individuals. Do not use these results to make medical decisions on your own: talk to a doctor or another qualified health professional about what your lean body mass means for you, especially before starting any diet, exercise program, medication dosing or weight-related treatment.