Body Fat Calculator
Estimate your body fat percentage from tape measurements using the US Navy circumference method.
Formula last reviewed 4 August 2026 · How we verify our calculators
Body fat
Updates live as you type
Frequently asked questions
It estimates body fat from tape measurements — neck and waist (and hips for women) plus height — using a logarithmic formula. No calipers or scales are required.
Measure the neck below the larynx, the waist at the navel for men and the narrowest point for women, and hips at the widest point. Keep the tape snug and level for consistent readings.
For most people it lands within a few percentage points of more advanced methods. Measurement technique is the biggest source of error, so measure carefully and repeat.
General fitness ranges are roughly 14–24% for men and 21–31% for women, varying with age. Athletes are often lower. Treat these as broad guides only.
No calipers, no scale — just a tape measure and two equations
A male, 175 cm tall, with a 38 cm neck and 85 cm waist, gets a body fat estimate of roughly 16.9% — squarely within the general fitness range — from nothing more than three tape measurements run through a logarithmic formula. A female at 165 cm, 33 cm neck, 75 cm waist and 95 cm hip comes out to roughly 26.9%. Notice the female calculation needed a fourth measurement the male one didn't: hip circumference. That's not an oversight — the US Navy circumference method genuinely uses two different equations for men and women, not one formula with a different constant plugged in. The male version works from waist minus neck; the female version needs waist plus hip minus neck.
Why a 1980s Navy fitness test still gets cited today
This method was developed for the US Navy specifically because it needed something field-usable — no calipers, no water-displacement tank, no lab technician, just a flexible tape measure and a formula anyone could apply consistently across thousands of personnel. Enter sex, height, neck and waist (plus hips if female), and the calculator runs the same logarithmic calculation.
The formula isn't where the error creeps in — your technique is
Every input here comes from a physical measurement, which means measurement technique matters more to accuracy than the formula itself. Measure the neck just below the larynx, the waist at the navel for men or at the torso's narrowest point for women, and hips at their widest point for the female calculation — keeping the tape level and snug without compressing the skin, and taking two or three readings to average out small errors. Because a single measurement can be off by enough to shift the result a percentage point or two, this method is far more useful tracked consistently over weeks than reacted to as a one-off number.
This is a general estimate, not medical advice. Consult a doctor or registered dietitian for personalised guidance.
Sources
- Hodgdon JA, Beckett MB (1984) — US Naval Health Research Center circumference-based body fat estimation, adopted as the US Navy body composition method