Most tape-measure body fat calculators hand you a number with two decimal places and let you assume it’s exact. It isn’t — and pretending otherwise is the opposite of useful.
Our body fat calculator uses the same published U.S. Navy method, with a few differences that matter:
- Instant — enter height, neck, waist (and hip, for women) and your estimate updates as you type, in inches or centimeters.
- Shareable — your measurements live in the page link, so you can send an exact result to a coach or your future self.
- Honest — we state the method’s real validation margin, about ±3–4 percentage points versus a DEXA scan, right in the explainer. A general estimate, not a diagnosis.
- Guarded — if your waist and neck measurements can’t produce a valid result, you get a friendly prompt to double-check your numbers instead of a confusing error.
Try it with your own measurements, and if you write about fitness, the calculator is embeddable on your own site with one iframe.