Body Fat % Estimator

It uses the U.S. Navy body-fat method, which estimates body-fat percentage from tape measurements — neck and waist for men, plus hips for women, against height. No calipers, scale, or scan required. The Navy developed it as a practical field method, so it trades some precision for needing nothing but a tape measure.

Men: essential below 6%, athletic 6–13%, fit 14–17%, healthy 18–24%, increased risk 25%+. Women (more essential fat physiologically): essential below 14%, athletic 14–20%, fit 21–24%, healthy 25–31%, increased risk 32%+. Very low body fat is not healthier than the athletic or fit range — some fat is essential for hormones and organ function.

It carries a margin of about ±3 to 4% against a DEXA scan, the reference standard, and is less accurate for very short stature, limb differences, or significant edema. Tape placement and breathing state affect the result, and it cannot separate visceral from subcutaneous fat. For most people it is close enough to be useful, especially for tracking change over time under consistent measurement.

Because it tells you what your weight is made of. Two people at the same weight and BMI can have very different body-fat percentages, and the health picture follows the fat, not the scale. It also lets you see recomposition — losing fat while gaining muscle — which the scale hides. Pair it with the Lean Body Mass Calculator to split weight into fat and lean mass.

Use a flexible tape, snug but not compressing the skin, at consistent landmarks: neck just below the larynx, waist at the navel, and (for women) hips at the widest point. Measure at the same time of day, take each measurement twice, and average. Because the estimate is sensitive to technique, consistency matters more than perfection — a repeatable method makes your trend reliable even if a single reading is a little off.