Measure consistently
Use measured height and weight and a body-fat estimate obtained under repeatable conditions; compare methods rather than selecting the most flattering result.
Lean-mass equation comparison
Compare lean body mass without calling it muscle mass.
Run Boer, James and Hume regressions beside a body-fat-derived estimate, then show method spread, implied fat mass and sensitivity to weight.
The calculation runs locally in this browser. Educational outputs do not replace professional assessment, diagnosis, treatment or emergency care.
Method and interpretation guide
Use the lean-mass result as a transparent estimate
Use measured height and weight and a body-fat estimate obtained under repeatable conditions; compare methods rather than selecting the most flattering result. The worksheet exposes its assumptions so the result can be checked instead of accepted as a black box.
Read the assumptions
Boer, James and Hume are population regressions. The body-fat method simply subtracts estimated fat mass, so it inherits the body-fat measurement’s error.
Escalate important decisions
A calculator cannot examine symptoms, medical history, medication effects or measurement quality. Use qualified professional guidance when the decision has health consequences.
Local calculation
Inputs are processed in this browser. No account or external calculator is required to produce the result.
False precision
Extra decimal places do not remove biological variation, input error or limits in the underlying population equation.
Scope
Boer, James and Hume are population regressions. The body-fat method simply subtracts estimated fat mass, so it inherits the body-fat measurement’s error.
Simple by design
Three steps to a clearer number.
Enter your details
Use realistic values in each field. You can change them anytime.
Calculate instantly
The formula runs locally, so there is no account or waiting time.
Use the result
Treat the answer as a practical estimate for your next decision.