F4Fitness Goal 4U Private by design Find a tool
Body Composition calculator

Lean Body Mass
Calculator

Estimate fat-free body mass from weight and circumference measurements. Use recent body measurements for a clearer body-composition estimate.

Start Lean Mass Explore Body Composition
100% privateInstant resultsNo sign-up
1Enter your details

Calculate your result

Use realistic, recent measurements for the most useful estimate.

Sex used by this formula
100% privateInputs stay in this browserInstant resultsCalculated in real timeNo sign-upFree to use
2Your result
Lean MassREADYStart with the form

Your result will appear here

Complete the form and select “Calculate result.” Your measurements never leave this page.

Educational estimate only—not medical advice.
Understand your result

How your Lean Mass estimate is created

A transparent overview of the inputs, method, and appropriate interpretation.

Evidence-informed Browser based
How it works

About this Lean Mass estimate

It estimates body-fat percentage from height and body circumferences, then subtracts estimated fat mass from total body weight to calculate lean body mass.

Circumference-based body composition method
Body measurements→Circumference model=Estimated Lean Mass
  1. 01Enter details
  2. 02Review inputs
  3. 03Use the estimate
Private by designNo account requiredInputs are not stored
Common questions

Lean Body Mass Calculator FAQ

Clear answers to help you understand and use your estimate.

01Is the Lean Body Mass Calculator free and private?

Yes. It is free, runs in your browser, requires no account, and does not store the measurements you enter.

02Can I use this result as medical advice?

No. This result is an educational estimate, not a diagnosis or treatment recommendation. A qualified professional can interpret it within your complete health and training context.

03Why might my Lean Mass result differ from a real-world result?

Tape placement, breathing, hydration, recent meals, body-fat distribution, and the population used to develop the equation can change the estimate.

04How often should I recalculate Lean Mass?

Recalculate when you take a new set of circumference measurements. Use the same tape positions and measurement conditions for a useful comparison.

Read our calculation methodology →Still have questions? Explore the guides ↗