Body Fat Calculator

Estimate your body fat percentage from a few tape-measure readings using the U.S. Navy method.

Used only for fat and lean mass.

Just below the larynx (Adam’s apple).

Men: at the navel. Women: at the narrowest point.

Body fat
18.4 %

18.4% falls in the "Average" range (ACE categories). Tape estimates are typically within 3–4 points of lab methods.

Body fat categories (men)
EssentialAthletes6Fitness14Average18Obese2518.4%
Category
Average
Fat mass
33.1
Lean body mass
146.9
Body composition
Fat mass: 15.012 (18.4%)Lean mass: 66.635 (81.6%)18.4%fat
  • Fat mass15.01218.4%
  • Lean mass66.63581.6%
Show the working
  1. Waist − neck = 88.9 − 39.4 = 49.5 cm
  2. Body density term = 1.05682
  3. Body fat = 495 ÷ 1.05682 − 450 = 18.4%

Runs entirely in your browser. Nothing you enter is uploaded.

Formula

Men: %BF = 495 ÷ (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450Women: %BF = 495 ÷ (1.29579 − 0.35004·log₁₀(waist + hip − neck) + 0.22100·log₁₀(height)) − 450All measurements in centimetres

How it works

The U.S. Navy method estimates body fat from circumference measurements. It was developed so recruiters could screen large numbers of people with nothing more than a tape measure, and it remains one of the more accurate do-it-yourself methods.

Measure on bare skin with the tape snug but not compressing the skin, and take each reading two or three times. Men measure the waist horizontally at the navel; women measure at the narrowest part of the waist and the widest part of the hips. Small measuring errors move the result noticeably, so consistency matters more than precision if you are tracking change over time.

Category labels follow the American Council on Exercise ranges. Essential fat (about 2–5% for men and 10–13% for women) is the minimum needed for normal body function; going below it is unhealthy. This calculator is for general information and is not medical advice.

Frequently asked questions

How accurate is the Navy method?

Compared with DEXA scans or hydrostatic weighing, it is usually within about 3–4 percentage points. It is less reliable for people with unusual fat distribution or very high or very low body fat.

Why does it need my weight?

It does not need it for the percentage. Weight is used only to split your body into fat mass and lean mass.

Is body fat a better measure than BMI?

For individuals, often yes — it separates fat from muscle, which BMI cannot. But both are screening tools; neither diagnoses a health problem on its own.

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