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Body fat calculator (US Navy method)

  

US Navy tape method. Typically within 3–4 points of a DEXA scan.

Sex

Units

cm
cm
cm

Body fat

18.6%

ACE category: Average.

How we got this

  1. waist − neck = 48 cm
  2. 495 ÷ (1.0324 − 0.19077 × log₁₀(48) + 0.15456 × log₁₀(170)) − 450 = 18.6%

Why measure fat, not only weight

Two people with the same BMI can carry very different amounts of fat. A tape estimate separates them cheaply. Measure at the same time of day each time, before eating.

For a weight target, compare with the ideal weight formulas, which use height alone.

Sources

What this calculator does not account for

  • Measuring error: a 1 cm slip in the waist moves the result by about 1 point.
  • Very lean or very heavy bodies, where the equations are least accurate.
  • Where the fat sits, which matters more for health than the total.

How this is calculated

Formula: US Navy circumference method

men: 495 ÷ (1.0324 − 0.19077 log₁₀(waist − neck) + 0.15456 log₁₀(height)) − 450

What the symbols mean

  • waist, neck, hipCircumferences in centimetres.
  • heightHeight in centimetres.

Good to know

  • Women: 495 ÷ (1.29579 − 0.35004 log₁₀(waist + hip − neck) + 0.221 log₁₀(height)) − 450.
  • Categories follow the American Council on Exercise bands.

Read the full methodologyFound an error? Contact us

Worked examples

Each example is worked out by the same code as the calculator above.

Man: 178 cm, neck 38, waist 86

waist − neck = 48 cm. The men's Navy equation with log₁₀ 48 and log₁₀ 178 gives 17.2%: the fitness band.

Woman: 165 cm, neck 33, waist 75, hips 98

waist + hip − neck = 140 cm. The women's Navy equation with log₁₀ 140 and log₁₀ 165 gives 28.4%.

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The frame shows the tool only.

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Questions

How accurate is the Navy method?

Within about 3 to 4 percentage points for most people. It is less reliable at very low or very high body fat.

Where exactly do I measure?

Neck just below the Adam's apple, waist at the navel for men or the narrowest point for women, hips at the widest. Keep the tape level and snug.

What is a healthy body fat percentage?

ACE lists 14–24% for men and 21–31% for women as fitness to average. Athletes run lower.