Body Fat Percentage Calculator

Everything is in centimetres. Men enter height, neck and waist. Women enter the same three plus hip, and the hip box only appears once you select Female. There is no weight box, because the method works from circumferences and height alone.

The defaults (male, 175 cm height, 38 cm neck, 85 cm waist) give 16.9%. A woman who is 165 cm tall with a 33 cm neck, 75 cm waist and 100 cm hip gets 29.4%. Either way the figure is an estimate from tape measurements, not a diagnosis and not a lab reading.

The tool uses the metric form of the US Navy circumference equations, as they are commonly published. They are attributed to Hodgdon and Beckett at the Naval Health Research Center (1984):

• Men: 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
• Women: 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450

These coefficients expect centimetres. Typing inches into the boxes does not just change the units; it produces a meaningless result. Convert first by multiplying inches by 2.54.

Small tape errors show up clearly in the result, which is why measuring the same way every time matters more than the exact spot:

A thicker neck lowers the estimate, because the men's formula works on waist minus neck. For the example woman, taking 1 cm off the waist moves her from 29.4% to 28.9%. Keep the tape level and snug without pressing into the skin, take each measurement twice, and use the average.

The tool stops at a percentage. To see it as mass, multiply by your weight. For the default man at 70 kg, 16.9% is about 11.9 kg of fat, which leaves about 58.1 kg of everything else.

The Lean Body Mass Calculator on this site gives 56.0 kg for the same height and weight, because it uses a different, weight-based formula. Neither is the true value. If you are tracking change over time, pick one method and stay with it rather than switching between them.

For men, the formula takes the logarithm of waist minus neck. If the neck is as large as the waist or larger, that value is zero or negative and the tool shows — instead of a number. It usually means a measurement went in the wrong box. For women the same happens only if waist plus hip doesn't exceed neck, which in practice points to a missing digit.