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SnapCalculations

Body Fat Calculator

All you need is a tape measure. Enter your height, neck and waist (plus hips for women) in inches or centimeters to estimate your body fat percentage.

Sex
Height in
ft
in
in

Just below the larynx (Adam's apple)

in

Around the navel (belly button)

Weight in
kg

Body fat

17.9%

Fitness

Fat mass
12.5 kg
Lean mass
57.5 kg

An estimate from tape measurements. Lab methods such as a DEXA scan are more accurate.

Step-by-step solution

Worked out with your numbers. Change any value above and the steps update.

  1. 1

    Waist minus neck (cm)

    86.4 − 38.1 = 48.3

  2. 2

    Body density part of the U.S. Navy formula

    1.0324 − 0.19077 × log₁₀(48.3) + 0.15456 × log₁₀(175.3) = 1.05801

  3. 3

    Body fat % = 495 ÷ density − 450

    495 ÷ 1.05801 − 450 = 17.9%

How it works

  • Uses the U.S. Navy circumference formulas, which estimate body density from height and neck, waist and hip measurements.
  • Men: 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450, with lengths in cm.
  • Women: 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.221 × log₁₀(height)) − 450.
  • Categories follow the American Council on Exercise ranges (for example, 18–24% is average for men and 25–31% for women).

Worked examples

Man, 178 cm

Estimate the body fat of a man 178 cm tall with a 38 cm neck and 90 cm waist.

  1. Waist − neck = 52 cm.
  2. Density part = 1.0324 − 0.19077 × log₁₀(52) + 0.15456 × log₁₀(178) = 1.05286.
  3. Body fat = 495 ÷ 1.05286 − 450.

Answer: About 20.1%: the “average” range for men

Try this example

Woman, 5 ft 5 in (inches)

Estimate the body fat of a woman 5 ft 5 in tall with a 13 in neck, 30 in waist and 39 in hips.

  1. Convert to cm: height 165.1, neck 33.02, waist 76.2, hips 99.06.
  2. Waist + hips − neck = 142.24 cm.
  3. Apply the women's U.S. Navy formula.

Answer: About 29.5%: the “average” range for women

Try this example

Frequently asked questions

How do I measure correctly?

Measure on bare skin with the tape level and snug but not tight. Men measure the waist at the navel; women at the narrowest point and the hips at the widest. Take each measurement twice and use the average.

How accurate is the Navy method?

It is a quick estimate, not a lab test. Results can be off by several percent, especially for very muscular people. DEXA scans and hydrostatic weighing are more accurate.

Can I enter weight in stone?

Yes. Choose “Stone & lb” for your weight. Weight is only used to work out fat mass and lean mass.

Results are estimates for general information and are not financial, medical or professional advice.