The U.S. Navy method estimates body fat from a few tape measurements and height. It uses the circumference equations developed for the Department of Defense by Hodgdon and Beckett, often called the Navy formula. For men it uses neck and abdomen; for women, neck, waist and hips. A man who is 70 in tall with a 15 in neck and a 34 in waist comes out at about 17.5% body fat.
It is popular because it needs only a tape measure, but it is an estimate. A 2003 cross-validation study in men who did not meet height-weight standards found the equation overpredicted body fat compared with hydrostatic weighing. Current Navy guidance (February 2025) has moved to a single-site abdominal measurement as a screening step and reads body fat from tables, so treat this as a tracking tool rather than an official assessment.
How to use the body fat calculator (u.s. navy method)
- Choose sex and whether you are measuring in inches or centimeters.
- Measure height without shoes.
- Measure the neck just below the larynx (Adam’s apple), with the tape sloping slightly down to the front.
- Men: measure the abdomen horizontally at the navel. Women: measure the waist at its narrowest point and the hips at the widest part of the buttocks.
- Take each measurement two or three times, relaxed and not sucking in, and use the average. Add your weight to see fat and lean mass.
Formula
All measurements are in inches; centimeter entries are divided by 2.54 first, because the constants were fitted to inches. Fat mass = weight × %BF; lean mass = weight − fat mass.
Worked example
Man: height 70 in, neck 15 in, abdomen 34 in, 175 lb.
- Abdomen − neck = 19; log10(19) = 1.27875; × 86.010 = 109.986.
- log10(70) = 1.84510; × 70.041 = 129.232.
- %BF = 109.986 − 129.232 + 36.76 = 17.5%.
- Fat mass: 175 × 0.175 ≈ 30.6 lb; lean mass ≈ 144.4 lb.
Woman: height 65 in, neck 13, waist 30, hips 38. %BF = 163.205 × log10(55) − 97.684 × log10(65) − 78.387 ≈ 28.6%.
Getting consistent results
Measurement technique matters more than the formula: a half-inch error at the waist moves the result by about 1 percentage point. Measure at the same time of day, before eating, with the same tape, and look at the trend over weeks rather than a single reading. Methods such as DEXA or hydrostatic weighing are more accurate but cost more.
Body fat complements BMI, which cannot tell muscle from fat. See the bmi calculator. Lean mass is a better guide to energy needs than total weight, though the bmr calculator uses weight, height and age.
Caveats and assumptions
- An estimate with a typical error of several percentage points; a 2003 validation found it overpredicted in some men.
- Not an official military body-composition assessment; current service rules use their own procedures and tables.
- Less reliable for very lean or very muscular people, older adults and during pregnancy.
- Not medical advice.
Frequently asked questions
How accurate is the Navy body fat formula?
It is a reasonable tape-measure estimate but can be off by several percentage points. A 2003 study found it overpredicted body fat versus hydrostatic weighing in men who did not meet height-weight standards.
Where do I measure my waist for the Navy method?
Men measure the abdomen at the navel. Women measure the natural waist at its narrowest point, plus the hips at the widest point of the buttocks.
Can I use centimeters?
Yes. Choose centimeters and the calculator converts to inches, which the equation constants require.
Why is a hip measurement only needed for women?
The DoD equations for women were fitted with waist, hip and neck; the men’s equation uses abdomen and neck only.
Sources
- Validity of the Navy circumference body fat equation in men. Med Sci Sports Exerc 2003 (abstract) — men’s equation and its tendency to overpredict
- U.S. Navy Physical Readiness Program — Guide 4: Body Composition Assessment (Feb 2025, PDF) — measurement sites; current table-based method (confirmed through search results)
- LibreTexts — The U.S. Navy body fat estimation formula — men’s and women’s equations in inches (confirmed through search results)
This calculator gives general estimates for healthy adults and is not medical advice, diagnosis or treatment. Equations are averages and individuals differ. Talk to a qualified health professional before changing your diet, exercise or medication, and during pregnancy. See our disclaimer and how we build and check calculators.