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Health & Fitness

Body Fat Calculator

Estimate your body fat percentage with the U.S. Navy tape measure method using your height, neck, waist and, for women, hip measurements.

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Units
Height
ft
in
Used only to show fat mass and lean mass.

Measure the neck just below the larynx, the waist at the navel for men or at the narrowest point for women, and the hip at its widest point.

Results are estimates based on the U.S. Navy method, not medical advice.

How to use the body fat calculator

Choose US (inches and pounds) or Metric (centimeters and kilograms) units and select your sex. Enter your height and your neck and waist measurements; women also enter their hip measurement. Weight is optional: if you add it, the calculator also shows your fat mass and lean mass. Press Calculate to see your estimated body fat percentage and its category.

How to measure

Use a flexible tape measure, keep it level and snug without pressing into the skin, and measure on bare skin. Take each measurement two or three times and use the average.

  • Neck: just below the larynx (Adam's apple), with the tape sloping slightly down toward the front.
  • Waist: for men, horizontally at the level of the navel; for women, at the narrowest part of the waist. Relax and do not pull your stomach in.
  • Hip (women): around the widest part of the buttocks.

The formula

The calculator uses the U.S. Navy circumference method developed by Hodgdon and Beckett. With all measurements in centimeters and log10 meaning the base-10 logarithm:

  • 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

Worked example

A man who is 178 cm tall with a 38 cm neck and an 86 cm waist has waist − neck = 48. The formula gives 495 / (1.0324 − 0.19077 × 1.6812 + 0.15456 × 2.2504) − 450 ≈ 17.2% body fat. If he weighs 80 kg, that is about 13.8 kg of fat mass and 66.2 kg of lean mass.

Body fat categories

The result is grouped using the categories published by the American Council on Exercise (ACE):

  • Essential fat: women 10–13%, men 2–5%
  • Athletes: women 14–20%, men 6–13%
  • Fitness: women 21–24%, men 14–17%
  • Average: women 25–31%, men 18–24%
  • Obese: women 32% and above, men 25% and above

Good to know

  • Tape measure methods usually land within a few percentage points of lab methods such as DEXA, but individual errors can be larger.
  • Small measuring mistakes, especially at the waist, can change the result noticeably, so measure carefully and at the same time of day when you track progress.
  • The method was developed for adults and may be less accurate for very muscular people, older adults and people with an unusual body shape.

The results are estimates and are not medical advice. For an accurate assessment, talk to a doctor or other qualified health professional.

Frequently asked questions

How accurate is the U.S. Navy body fat method?

For most adults it gives an estimate within roughly three to four percentage points of laboratory methods. Accuracy depends heavily on careful measuring, and the error can be larger for very lean, very muscular or very heavy people.

Why do women need a hip measurement?

Women tend to store more fat around the hips and thighs. The female version of the U.S. Navy formula includes the hip measurement to account for this, while the male version uses only the neck and waist.

Why does the calculator say my waist must be larger than my neck?

The formula takes the logarithm of waist minus neck (or waist plus hip minus neck for women). That value must be positive, so a waist smaller than the neck usually means a typing mistake or a mix-up between inches and centimeters.

What is a healthy body fat percentage?

Ranges depend on sex and age. According to the ACE categories, about 21–31% for women and 14–24% for men falls in the fitness to average range. Going below essential fat levels can be harmful to health.