Body fat calculator
This calculator estimates your body fat percentage from a few tape measurements, using the US Navy method. All you need is a flexible tape measure, no calipers or scans required.
How is this estimate calculated?
The US Navy method uses circumference measurements at your neck and waist (and hips, for women) along with your height to estimate body fat percentage. It was developed for quick, equipment-free fitness assessments. It's repeatable and easy to do at home, but studies comparing it with lab methods find individual results can miss by several percentage points, so small changes between measurements are often just noise.
Source: Hodgdon JA, Beckett MB. "Prediction of Percent Body Fat for U.S. Navy Men and Women from Body Circumferences and Height." Naval Health Research Center, San Diego, Reports No. 84-11 and 84-29, 1984.
Frequently asked questions
How does the tape measurement method work?
This calculator uses the US Navy method, which estimates body fat percentage from your neck, waist, and (for women) hip circumference, along with your height. It's not as precise as a DEXA scan, but it's a reasonable, repeatable estimate you can do at home.
Where exactly should I measure?
Measure your neck just below the larynx, your waist at the narrowest point (or at the navel if there's no clear narrowing), and your hips at the widest point. Keep the tape snug but not compressing the skin.
How accurate is this compared to a DEXA scan or calipers?
It's an estimate, and for any one person it can be off by several percentage points compared with lab methods. Circumference equations tend to underestimate body fat at higher levels and overestimate it at lower levels, and lab methods like DEXA carry their own error too. The Navy method is most useful for tracking your own trend over time, measured the same way each time, rather than as an exact number.
How often should I retest?
Body fat changes slowly. Retesting every 4-6 weeks, using the same measurement spots each time, gives a much more useful trend than checking weekly.