Body Fat Calculator

The US Navy body fat formula

This tool estimates body fat percentage with the US Navy circumference method, which only needs a tape measure. For men the metric formula is %BF = 495 / (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450. For women it adds the hip measurement: %BF = 495 / (1.29579 − 0.35004·log₁₀(waist + hip − neck) + 0.22100·log₁₀(height)) − 450. All measurements are in centimeters. When you choose imperial units, inches are converted to centimeters before the formula is applied, so the result is identical either way.

The method works because fat distributes around the waist and hips in predictable ways relative to neck and height. By comparing those circumferences it produces a quick body fat estimate without calipers, a scale or a lab. If you enter your body weight, the calculator also splits your total mass into estimated fat mass and lean mass so you can track changes over time.

Reading your result

Body fat categories differ for men and women because women carry more essential fat. A common guide for men is roughly 2–5% essential, 6–13% athletic, 14–17% fitness, 18–24% average and 25% or more in the higher range. For women the bands sit higher: about 10–13% essential, 14–20% athletic, 21–24% fitness, 25–31% average and 32% or more higher. Use these as conversation starters rather than strict cut-offs.

Accuracy and a health note

Tape methods depend on consistent measuring. Pull the tape snug but not tight, keep it level, and measure at the same points each time so trends are meaningful. Expect an estimate within a few percent of lab methods like DEXA. This page is for general information only and is not medical advice. If you have health concerns or are setting goals for a medical reason, talk to a qualified professional. Nothing you enter is uploaded; the calculation runs entirely in your browser.