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Calculate your Lean Body Mass
This calculator uses the Boer formula, which estimates lean body mass from weight, height, and gender. For men and women, different coefficients account for typical body composition differences. Your body fat percentage is then used to calculate fat mass and lean mass separately.
Lean body mass is a more meaningful fitness metric than total body weight because it reflects your muscle, bone, and organ mass without fat. Tracking LBM helps you distinguish between fat loss and muscle loss during a diet, ensuring you are making healthy progress.
The result shows your lean mass (everything except fat), fat mass, body fat percentage, and an estimated Basal Metabolic Rate (BMR). A higher lean mass relative to total weight generally indicates better fitness. The BMR estimate shows how many calories your body burns at rest.
Track your LBM over time to monitor muscle gains or losses rather than focusing solely on scale weight. Combine this with strength training to preserve and build lean mass. For the most accurate body fat percentage input, consider using calipers or a DEXA scan.
Lean body mass (LBM) is your total body weight minus all fat weight. It includes muscle, bones, organs, skin, blood, and water - everything in your body that is not fat tissue. For most people, lean body mass makes up 60-90% of total body weight. LBM is an important metric for fitness because it reflects your functional tissue mass and is a better indicator of fitness than total body weight alone.
To increase lean body mass, focus on progressive resistance training (weightlifting) at least 2-4 times per week, targeting all major muscle groups. Consume adequate protein (1.6-2.2 grams per kilogram of body weight daily) to support muscle growth. Eat in a slight caloric surplus (200-500 calories above maintenance) to fuel muscle building. Get 7-9 hours of quality sleep for recovery and hormone optimization. Stay consistent over months, as building lean mass is a gradual process.
Total body weight is everything on the scale, including both fat mass and lean mass. Lean body mass excludes all fat tissue. This distinction is important because two people can weigh the same but have very different body compositions. Someone with more lean mass and less fat will generally be healthier and more fit. Tracking lean body mass rather than total weight helps you ensure that weight changes come from fat loss rather than muscle loss, especially during a diet.