Lean Body Mass Calculator
Estimate lean mass and fat mass from height and weight using the Boer formula.
An estimate from a height-and-weight formula, not a body composition scan — it can't see muscle vs. fat directly. Not medical advice.
Lean body mass (Boer formula)
60.9 kg
Estimated fat mass
19.1 kg
Estimated fat percentage
23.9%
For informational and educational purposes only — not medical advice, and not a substitute for consulting a qualified professional about your specific situation. TrueMeasureKit is not liable for decisions made based on these results. See our Terms of Service.
Why lean mass, not just weight, is the useful number
The Boer formula, published in 1984, is widely cited as the most accurate of the height-and-weight-only lean mass estimates — more accurate than the older James or Hume formulas for most body types, though all three are approximations next to a DEXA scan. Lean mass includes muscle, bone, organs, and water — everything that isn't fat — which is why it's a more stable number to track over a diet or training block than total body weight alone: it stays roughly constant while fat mass moves, so tracking the split shows whether weight change is coming from fat loss or muscle loss.
Frequently asked questions
What is the Boer formula this calculator uses?
A widely used equation that estimates lean body mass from height and weight, with separate formulas for men and women, developed by P. Boer in 1984 and still commonly used as a quick, no-equipment estimate.
How does this differ from a body fat percentage measurement?
Lean body mass is an absolute weight (muscle, bone, organs, water — everything except fat), while body fat percentage is fat as a share of total weight. This calculator derives both from the same height/weight inputs.