Navy Body Fat Calculator (Tape Measure Method)
Estimate adult body fat percentage with the historical Navy circumference equation from height, neck, waist and hips, plus fat mass and lean mass.
The U.S. Navy method estimates body fat from a few tape-measure readings and your height. The equations were fitted against underwater weighing at the Naval Health Research Center and have long been used in military body-composition checks, because they need only a cloth tape. It is a practical way to track change without a DEXA scan or calipers.
How to use this tool
- Choose your sex and whether you measure in inches or centimetres.
- Measure your height barefoot.
- Measure the neck just below the larynx, with the tape sloping slightly down towards the front.
- Men: measure the waist level with the navel. Women: measure the waist at its narrowest point and the hips around the widest part of the buttocks.
- Add your weight if you want fat mass and lean mass as well.
Formula
Men: %BF = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Women: %BF = 163.205 × log₁₀(waist + hips − neck) − 97.684 × log₁₀(height) − 78.387
All lengths in the equations are inches; centimeters are divided by 2.54 first. log10 is the base-10 logarithm. Estimated fat mass equals body weight multiplied by the percentage divided by 100. The remainder is fat-free mass, which includes water, bone and organs as well as muscle.
Example
A man 70 in tall with a 15 in neck and a 34 in waist has waist − neck = 19 in. 86.010 × log₁₀(19) = 109.99 and 70.041 × log₁₀(70) = 129.23, so body fat = 109.99 − 129.23 + 36.76 ≈ 17.5%. At 180 lb that is about 31.5 lb of fat and 148.5 lb of lean mass.
Frequently asked questions
How accurate is the Navy body fat method?
It is an estimate. Circumference equations match group averages well but can be several percentage points out for one person, especially very muscular people or anyone who carries fat mainly on the hips and thighs. Measure at the same spots and time of day, and judge the trend rather than a single reading.
Why do women need a hip measurement?
Women store proportionally more fat around the hips and thighs, so the women’s equation adds hip circumference to the waist. The men’s equation uses only waist and neck.
Is this the official military tape test?
These are the classic Navy equations. The services have revised their rules over the years and some now use different tape tests, so check your current instruction before an official assessment.
What body fat percentage is healthy?
There is no single percentage that establishes health for everyone. This page gives a numerical estimate without a diagnostic category. Age, health, body shape and the measurement method affect interpretation; a very low or high result needs checking.
Sources
This tool gives an estimate for general information only. It is not financial, tax, legal or medical advice — check with a qualified professional before you rely on the result.
Last updated: 2026-10-30