Lean Body Mass Calculator Online

Your measurements

Choose your units, then enter the details you want to use.

Your estimate will appear here

Complete the relevant fields and select Calculate. Changes to your inputs clear the previous result.

Educational estimates, with their equations and assumptions. They do not diagnose a condition or prescribe a treatment.

Method, assumptions & sources

Who this is for

Adults aged 20 or older, outside pregnancy and breastfeeding; educational estimates for generally healthy adults.

How it works

Janmahasatian (2005): male fat-free mass (kg) = 9270W ÷ (6680+216 BMI); female = 9270W ÷ (8780+244 BMI). W is kg and BMI is kg/m². This implementation accepts BMI 17–70 and rejects estimates exceeding total weight.

Keep in mind

Fat-free mass includes organs, water and bone; it is not muscle mass.
Do not use for medication dosing, pregnancy, significant fluid retention or unusual body composition.

Sources

Janmahasatian et al. (2005): quantification of lean bodyweight (opens in a new tab)