Body Fat Calculator
Estimate body fat percentage from tape measurements with the US Navy method.
How it works
Choose the sex used by the formula and enter your height, neck and waist measurements, plus hip for women. Measure the neck just below the larynx, the waist at the navel (men) or narrowest point (women), and the hip at its widest point.
Lengths in cm:
male BF% = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
female BF% = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450Example
A man 175 cm tall with a 38 cm neck and 85 cm waist: waist − neck = 47. The denominator is 1.0324 − 0.19077 × 1.6721 + 0.15456 × 2.2430 = 1.0601, so BF% = 495 ÷ 1.0601 − 450 = 16.9%.
Common mistakes
- Measuring over clothing or pulling the tape tight enough to compress the skin. Keep it snug and level.
- Measuring the waist in the wrong place. The method expects the navel for men and the narrowest point for women.
- Reading the result as exact. It is an estimate, and other methods may differ by several percentage points.
Results are estimates and are not a substitute for medical advice.
About this calculator
The US Navy method estimates body fat from tape measurements. For men it uses height, neck and waist. For women it also uses hip. Imperial entries are converted to centimetres before the formula is applied.
The result is an estimate, and it is usually off by a few percentage points for any one person. Measurement position matters, and the method does not measure fat directly. If the measurements give a result outside about 2–60%, no figure is shown.
Frequently asked questions
How accurate is the US Navy method?
It is a rough estimate that is typically off by a few percentage points for an individual. It is useful for tracking your own measurements over time, not for a precise reading.
Why does it ask for hip only for women?
The female version of the formula includes hip: BF% = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. The male version does not use it.
Why do I see a message instead of a percentage?
If the measurements give a result outside about 2–60%, the method is not reliable, so the calculator shows a message instead of an odd number. Re-check the measurements first.
What are the reference ranges?
They are commonly quoted bands (essential, athletes, fitness, average, above average) and differ between men and women. Treat them as a rough guide; other sources draw the lines differently.