Body Fat Calculator
Estimate your body fat percentage from a tape measure using the US Navy method, with ACE category ranges for men and women in metric or imperial units.
This is a body-composition estimate for general information, not medical advice. For a diagnosis or health decisions, speak to a qualified professional.
How the Navy method works
The US Navy circumference method estimates body fat from the idea that fat gathers in
predictable places - the waist for men, the waist and hips for women - relative to the neck
and overall height. It plugs your tape measurements into a logarithmic formula. For men that
is 495 / (1.0324 - 0.19077 x log10(waist - neck) + 0.15456 x log10(height)) - 450,
with all lengths in centimetres. Women use waist plus hip minus neck instead. No scales, no
calipers, no clinic - just a tape measure.
Measuring well
The answer is only as good as the tape work. Measure on bare skin, keep the tape level and snug without digging in, and take each measurement two or three times to average out wobble. Neck goes just under the Adam's apple; the male waist is at the navel; the female waist is at the narrowest point and the hip at the widest. A centimetre of slack on the waist can move the result by a percentage point, so be consistent every time you re-measure.
ACE body fat categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2-5% | 10-13% |
| Athletes | 6-13% | 14-20% |
| Fitness | 14-17% | 21-24% |
| Average | 18-24% | 25-31% |
| Obese | 25%+ | 32%+ |
Accuracy and caveats
Against a DEXA scan, the gold standard, the Navy method is typically within 3 to 4 percentage points for average builds, and less reliable at the extremes - very lean, very muscular, or very heavy. It cannot tell where fat sits internally. Treat the number as a repeatable trend line rather than an exact truth: measured the same way each month, it is a genuinely useful way to see change. To sense-check overall weight, pair it with the BMI calculator, and to plan intake use the calorie calculator.