Body fat calculator
The tape method is only as good as the tape work. Measure first thing in the morning before eating, keep the tape level and snug without compressing, and take the waist at the navel rather than at the narrowest point. Repeatability matters more than absolute accuracy: this method is roughly ±3 percentage points against a DEXA scan, but it tracks change reliably if you measure consistently.
Bands differ by sex; the category row above uses the correct set for the sex selected.
A tape-measure estimate, accurate to roughly ±3 percentage points against a DEXA scan. It is far better at tracking change over time than at giving an exact figure.
The US Navy method estimates body fat from height and circumference measurements — neck and waist for men, plus hips for women. It is accurate to about ±3 percentage points against a DEXA scan and needs nothing but a tape measure.
How to measure body fat with a tape
Circumference methods work because fat distributes in predictable places, and the difference between waist and neck carries most of the signal. What they cannot do is distinguish an unusual build: someone with a very thick neck from training will read leaner than they are, and someone with a naturally narrow one will read fatter. Because those errors are consistent for a given person, the method is markedly better at tracking a trend across weeks than at pinning down a single number.
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Roughly ±3 percentage points against DEXA. Consistent technique makes it reliable for tracking change.