Body Fat Calculator
Estimate your body fat percentage with just a tape measure, using the U.S. Navy circumference formula — plus fat mass and lean mass if you add your weight.
Just below the larynx (Adam's apple).
Horizontally at the navel.
Only used to estimate fat mass and lean mass.
Uses the U.S. Navy circumference method (Hodgdon & Beckett, 1984), which estimates body fat from height, neck and waist (plus hip in the female formula). It's an estimate: compared with lab methods such as DEXA it's typically within a few percentage points for many people, but a 1 cm error in the waist measurement can move the result by roughly a point. Measure relaxed, on bare skin, and take the average of several readings. This isn't a medical assessment.
17.2%
Estimated body fat
Add weight
Fat mass (kg)
Add weight
Lean mass (kg)
Everything you enter is processed in your browser and isn't sent to our servers.
How to use body fat calculator
- 1Choose the male or female formula and your preferred units.
- 2Measure your height, neck and waist (and hips for the female formula) with a flexible tape.
- 3Optionally enter your weight to see estimated fat mass and lean mass.
- 4Read your estimated body fat percentage.
About this tool
The U.S. Navy method (Hodgdon & Beckett, 1984) estimates body fat from circumference measurements, because fat around the waist and hips changes those measurements far more than muscle does. The male formula uses waist minus neck and height; the female formula uses waist plus hip minus neck, and height.
In centimetres, the male formula is 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450, and the female formula is 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. Inch measurements are converted to centimetres first.
It's an estimate. For many people it lands within a few percentage points of lab methods like DEXA, but it can be less accurate for very muscular or very lean people, and small measuring errors matter: being 1 cm off at the waist can shift the result by about a point. Measure on bare skin, relaxed, at the same spots each time, and average several readings. This tool doesn't diagnose anything and isn't medical advice.
Frequently asked questions
Neck: just below the larynx (Adam's apple), with the tape sloping slightly down at the front. Waist: at the navel for the male formula, or the narrowest point of the waist for the female formula. Hips: the widest point of the buttocks. Keep the tape snug but not compressing the skin.