Gauritanaya

Body fat calculator

Two published tape-measure methods side by side, so you can see how much the estimate varies.

Runs entirely in your browser. Nothing you type is sent anywhere.

Height
cm
Weight (optional, for fat and lean mass)
kg
Waist
cm

Men: measure at the level of the navel. Women: measure at the narrowest point.

Neck
cm

Measure just below the larynx (voice box).

Hips (women)
cm

Measure around the widest part of your buttocks.

Body fat, US Navy method—

Body fat, Relative Fat Mass
—
Fat mass (Navy)
—
Lean mass (Navy)
—
Lean body mass (Boer formula)
—

Tape-measure methods are estimates. Lab methods such as DEXA are more accurate, and results can differ by several percentage points.

For general wellness only. These results are estimates from published formulas and guidelines, not a diagnosis or medical advice. They may not suit pregnancy, children, older adults, athletes or people with health conditions. Talk to a qualified health professional about your health. In an emergency, call your local emergency number.

How to use the body fat calculator

US Navy method (Hodgdon and Friedl, 1999; measurements in inches): men %BF = 86.010 × log10(abdomen − neck) − 70.041 × log10(height) + 36.76; women %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387. Relative Fat Mass (Woolcott and Bergman, 2018): 64 − 20 × height ÷ waist for men, 76 − 20 × height ÷ waist for women. Boer lean body mass: men 0.407 × kg + 0.267 × cm − 19.2; women 0.252 × kg + 0.473 × cm − 48.3.

  1. Choose units and your sex.
  2. Enter your height, and your weight if you want fat and lean mass.
  3. Measure your waist and neck (and hips for women) with a flexible tape, snug but not tight.
  4. Compare the two estimates.

Understanding your result

You get two estimates from two published tape-measure methods; the gap between them shows how uncertain such estimates are. We don’t label the result healthy or unhealthy, because we haven’t found ranges agreed across ages, sexes and ethnic groups. Track the same method over time to see change.

Sources

Sources checked on 9 October 2026. Formulas and thresholds are used as published; the wording on this page is our own.

Questions

Why do the two methods give different numbers?
They were built from different groups of people with different measurements. Seeing both shows you the uncertainty in any tape-measure estimate.
Why doesn’t this tool say whether my body fat is healthy?
We haven’t found body-fat ranges that are agreed across ages, sexes and ethnic groups, so the tool shows the estimate only. Your waist-to-height ratio is a simpler, well-supported check.
How can I measure more consistently?
Measure at the same time of day, on bare skin, with the tape level and snug. Take each measurement twice and use the average.
Is this a diagnosis?
No. It compares your numbers with published ranges for general wellness. Only a qualified health professional can assess your health, taking your history and other tests into account.

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