Body fat percentage can be estimated with a tape measure using the US Navy method: from your height and your neck and waist measurements (and hips, for women). Average body fat is 18 to 24% for men and 25 to 31% for women, according to the American Council on Exercise; 25% or more for men and 32% or more for women is classed as obese.
Enter your sex, height and measurements. The calculator gives the Navy estimate, the relative fat mass (RFM) estimate from height and waist, and — if you add your weight and age — the BMI-based estimate, so you can see how closely they agree.
Worked example
Sex: MaleAge: 40 yearsHeight: 5 ft 10 inWeight: 180 lbNeck: 15.5 inWaist: 34 in
Body fat (US Navy method): 16.5% Fitness
A 5 ft 10 in man with a 15.5-inch neck and a 34-inch waist is at about 16.5% body fat by the Navy method — the "fitness" range. Relative fat mass puts him at 22.8%. The BMI-based estimate, 24%, is higher again, because BMI counts muscle as fat.
Open this example in the calculator →How to use the Body Fat Calculator
- Choose your sex and US or metric units, and enter your height.
- Measure your neck just below the Adam’s apple and your waist — at the belly button for men, at the narrowest point for women.
- Women: measure your hips around the widest part.
- Optionally add weight and age, then read your body fat percentage and category.
How to measure
- Use a soft tape, snug against the skin but not pressing in, and keep it level all the way around.
- Neck: just below the larynx (Adam’s apple), with the tape sloping slightly down toward the front. Don’t flare your neck.
- Waist: men at belly-button level; women at the narrowest point between the ribs and hips. Stand relaxed and measure at the end of a normal breath out.
- Hips (women): around the widest part of the buttocks, feet together.
- Measure two or three times and use the average. Round to the nearest half inch or centimeter.
The formulas
US Navy (Hodgdon and Beckett, 1984), in centimeters:
- Men: body fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
- Women: body fat % = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
Relative fat mass (Woolcott and Bergman, 2018): 64 − 20 × height ÷ waist for men, 76 − 20 × height ÷ waist for women. It needs nothing but a height and a waist, and in its validation study it matched DEXA scans better than BMI did.
BMI-based (Deurenberg, 1991): 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, with sex = 1 for men and 0 for women. It cannot tell muscle from fat, so it reads high for muscular people.
Body fat percentage chart (ACE)
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | 32% or more | 25% or more |
Women need more essential fat than men, for hormones and reproduction. Body fat rises with age in both sexes, and these categories do not adjust for it.
Body fat or BMI?
Body fat measures what BMI only stands in for, so for one person it is more informative — if it is measured well. Since 2025, an international commission in The Lancet Diabetes & Endocrinology has recommended confirming obesity with a direct measure of body fat or a waist measurement rather than relying on BMI alone. For a quick check, a waist under half your height is a good sign; see the waist-to-height ratio calculator.
How accurate are home methods?
Against laboratory methods, the Navy formula is typically within about 3 to 4 percentage points, RFM similar, and bathroom bioimpedance scales vary more with hydration. DEXA scans, underwater weighing and air-displacement (Bod Pod) are the reference methods. For tracking progress, consistency matters more than the method: use the same one, measured the same way.
Frequently asked questions
What is a healthy body fat percentage?
The American Council on Exercise puts average at 18 to 24% for men and 25 to 31% for women, fitness at 14 to 17% and 21 to 24%, and obese at 25% or more for men and 32% or more for women.
How accurate is the US Navy body fat method?
Usually within 3 to 4 percentage points of a lab measurement such as DEXA, if the tape is placed carefully. Small measuring errors at the neck or waist change the result noticeably, so measure twice.
What is relative fat mass (RFM)?
A 2018 formula that estimates body fat from height and waist alone: 64 − 20 × height ÷ waist for men, and 76 − 20 × height ÷ waist for women. In its validation study it predicted DEXA body fat better than BMI.
Why do the three results differ?
Each is an estimate from different measurements. The Navy and RFM methods use the waist, which tracks fat; the BMI-based estimate uses weight, which includes muscle, so it reads high for muscular people. Close agreement between methods is a good sign.
How can I measure body fat at home?
A tape measure with the Navy method is the cheapest reliable option. Skinfold calipers work well with practice. Bioimpedance scales are convenient but vary with hydration, so weigh at the same time each day.
What body fat percentage shows abs?
Visible abdominal muscles usually appear at roughly 10 to 12% for men and 16 to 20% for women, but it depends on genetics and where you store fat.
Sources
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, Reports 84-11 and 84-29 — Naval Health Research Center
- Woolcott OO, Bergman RN. Relative fat mass (RFM) as a new estimator of whole-body fat percentage. Sci Rep 2018;8:10980 — Scientific Reports
- Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr 1991;65:105–114 — British Journal of Nutrition
- Percent Body Fat Calculator and categories — American Council on Exercise
- Rubino F et al. Definition and diagnostic criteria of clinical obesity. Lancet Diabetes Endocrinol 2025;13:221–262 — The Lancet Diabetes & Endocrinology
- AMA: Use of BMI alone is an imperfect clinical measure (2023) — American Medical Association
For general information only — not a diagnosis or a substitute for advice from a doctor. How we calculate.