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Lean Body Mass Calculator

Everything that isn't fat: muscle, bone, organs and water.

Reviewed by the Calculation Machine team · How we check our maths

Your values

ⓘ Live results

Results
Lean body mass
130 lb
Fat mass
40 lb
Body fat
23.5%
Fat-free mass index
19.2

Quick answer

Lean body mass is total weight minus fat mass; the Boer formula estimates it from height and weight alone.

The formula

Male LBM = 0.407·kg + 0.267·cm − 19.2

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • UnitsImperial (lb, in)
  • Weight170
  • Height69
  • SexMale

Result

  • Lean body mass130 lb
  • Fat mass40 lb
  • Body fat23.5%
  • Fat-free mass index19.2

How to use the Lean Body Mass Calculator

  1. 1Choose your units.
  2. 2Enter weight, height and sex.
  3. 3Read lean mass and estimated fat mass.

Frequently asked questions

Why track lean mass?

During a diet it shows whether you are losing fat or muscle, which weight alone cannot tell you.

What is a good FFMI?

Around 19–21 for trained men and 15–17 for trained women; above 25 without drugs is very rare.

About this calculator

Why lean body mass matters

Lean body mass is everything except fat — muscle, bone, organs and water. It drives your metabolic rate and is the better base for setting protein targets and some drug doses.

The calculator estimates it with the Boer, James and Hume formulas from height, weight and sex. These are population estimates; a body-fat measurement gives a more personal figure.

Using the estimate

  • Protein targets based on lean mass avoid overestimating needs for people with high body fat.
  • To see real change, track lean mass every few months rather than weekly.
  • Losing weight slowly with strength training protects lean mass.

Sources

More questions

Is lean body mass the same as muscle mass?

No. Muscle is only part of it; bone, organs and water make up the rest.

Which formula should I use?

Boer is often preferred for adults of normal build; results differ only by a few kilograms.