Lean Body Mass Calculator

Estimate your lean (fat-free) body mass and fat mass from your height, weight and sex using the Boer formula.

Read the guide: Lean Body Mass: Why It Matters More Than Weight

Your measurements

Units
Sex

Lean body mass

61.4 kg

76.8% of your body weight

Fat mass
18.6 kg
Lean percent
76.8%

Lean mass

61.4 kg

  • Lean mass77%
  • Fat mass23%

Estimated with the Boer formula. A body scan is more precise. Informational only, not medical advice.

How it works

  1. 1

    Pick units and sex

    Choose metric or imperial and your sex.

  2. 2

    Enter height and weight

    Add your measurements.

  3. 3

    See the split

    View your lean mass, fat mass and lean percentage.

Instant & 100% private — nothing is uploaded

Every calculation runs locally in your browser. The measurements, dates and details you enter stay on your own device and are never sent to a server — nothing is stored, logged or shared.

Frequently asked questions

What is lean body mass?
It is everything that is not fat — muscle, bone, organs and water. Tracking it helps you tell whether weight change is muscle or fat.
Why does lean mass matter?
Lean mass drives your metabolism and strength. When losing weight, keeping lean mass (with protein and resistance training) is the goal; when building, gaining it is.
Is this medical advice?
No. These calculators are for general information and education only. They are not a diagnosis or a substitute for professional care — talk to a doctor or qualified clinician about your health.