Lean Body Mass Calculator

How lean body mass is calculated

Lean body mass (LBM) represents everything in your body that is not fat: muscle, bone, organs, water, and connective tissue. The Boer, James, and Hume formulas estimate LBM using height, weight, and sex, which is why they are popular for quick, non-invasive comparisons.

What to do with the three estimates

• Boer: A widely used equation for adults that balances height and weight.
• James: Adjusts more aggressively for body weight relative to height.
• Hume: Another clinically validated equation used in health research.

Treat the results as a range. Small gaps between formulas are normal, so focus on the trend over time rather than a single snapshot.

Why add body fat percentage?

If you know your body fat %, we estimate fat mass directly and show the remaining lean mass. This is useful for comparing formula-based LBM to measurements from bioimpedance scales or a DEXA scan.

Next steps

Use BiteCheck to log your lean mass and body fat estimates, then map them to calorie targets, protein intake, and strength goals. Combine this with the body fat and BMI calculators for a fuller body composition check-in.