Navy Body Fat Calculator
The US Navy circumference method, using a tape measure and nothing else.
Measurements
Estimated body fat
What the tape method can and cannot do
The US Navy method estimates body fat from circumference measurements and height, using a logarithmic equation fitted to a large military sample. Men need neck and waist; women also need hips, because female fat distribution is not predicted well by the waist alone. The metric and imperial versions use completely different coefficients — applying the imperial equation to centimetres is a common bug that produces wildly wrong answers.
Accuracy is around ±3-4 percentage points against DEXA for people of typical build, which is adequate for tracking change over time and poor for a single authoritative figure. It degrades at the extremes: very lean and very muscular people tend to read high, because a thick neck or a muscular waist is interpreted as girth. It also cannot distinguish visceral from subcutaneous fat.
Consistency matters more than precision. Measure at the same time of day, ideally in the morning before eating, with the tape snug but not compressing. Take each measurement three times and use the median. The trend over weeks is the useful signal — a single reading carries more measurement error than most people expect, and chasing week-to-week noise is a good way to draw wrong conclusions.
Medical disclaimer. This calculator is for general information and education only. It is not medical advice, not a diagnosis, and not a substitute for professional care. Circumference estimates are screening tools rather than clinical measurements, and they read inaccurately for very lean, very muscular, and pregnant individuals.Speak to a doctor or another qualified clinician about any health decision.Last reviewed .
Frequently asked questions
How accurate is the Navy body fat method?
Roughly ±3-4 percentage points against DEXA for people of typical build. It is good for tracking change over time and less reliable as a single authoritative number, particularly at very low or very high body fat.
Why do women need a hip measurement?
Because female fat distribution is not predicted well by waist circumference alone. The female equation uses waist plus hip minus neck, which captures the gynoid pattern that a waist-only measurement would miss.
Where do I measure my neck and waist?
Neck just below the larynx, with the tape sloping slightly downward at the front. Waist at the navel for men, and at the narrowest point for women. Stand relaxed and measure at the end of a normal exhale.
What is a healthy body fat percentage?
Commonly cited ranges are about 8-19% for men and 21-32% for women, with athletes often lower. Essential fat — the minimum required for normal function — is around 3% for men and 12% for women, and sustained levels near that are not healthy.
Why does it read high for muscular people?
The equation interprets girth as fat. A muscular neck, back or waist adds circumference without adding fat, so the estimate overshoots. The same applies in reverse for people with low muscle mass, where it can read low.