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Body Fat Calculator

Estimate your body fat percentage with nothing more than a tape measure. This calculator uses the U.S. Navy circumference method published by Hodgdon and Beckett: neck, waist and height for men, plus hips for women. It shows the logarithmic formula with your measurements, places the result in the American Council on Exercise categories and, if you add your weight, splits it into fat mass and lean mass.

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Estimate Your Body Fat Percentage

General information, not medical advice. Tape-measure estimates are approximate and not suitable for children or pregnancy.

The published equations have separate versions for men and women.
cm
cm
cm
kg
Adds fat mass and lean mass.

How to Use the Body Fat Calculator

  1. Choose metric or imperial units and your sex.
  2. Measure height, neck (just below the larynx), waist (men: at the navel; women: at the narrowest point) and, for women, hips at the widest point.
  3. Optionally enter your weight, then press Calculate.

About This Tool

Adults tracking body composition alongside weight, fitness coaches, and people who want a cheaper alternative to smart scales or calipers.

Input: Body measurements  ·  Output: Body fat %.

Features and Limitations

Features

  • Names and shows the U.S. Navy formula with each logarithm.
  • Works in centimetres or inches.
  • ACE category table with your band highlighted.
  • Optional fat-mass and lean-mass split.

Limitations

  • Typically within about 3–4 percentage points of laboratory methods, but less accurate for very lean, very muscular or older people.
  • Small measuring errors change the result noticeably; measure twice and average.
  • Not for children, teenagers or pregnancy.
  • Results are computed in your browser; nothing you enter is sent to a server.

Example

A man 180 cm tall with a 40 cm neck and 90 cm waist: 495 ÷ (1.0324 − 0.19077 × log10(50) + 0.15456 × log10(180)) − 450 ≈ 18.4% body fat, in the “Average” band.

Frequently Asked Questions

How accurate is the Navy body fat method?

Studies comparing it with DEXA and hydrostatic weighing usually find average errors of about 3–4 percentage points, which is similar to bioimpedance scales.

Where exactly should I measure?

Neck just below the Adam’s apple, sloping slightly down at the front; waist horizontally at the navel for men and at the narrowest point for women; hips at the widest point of the buttocks. Keep the tape snug but not tight.

Why do women need a hip measurement?

Women typically store more fat around the hips and thighs, so the women’s equation adds the hip circumference to improve accuracy.

What is a healthy body fat percentage?

ACE lists 14–24% as fitness to average for men and 21–31% for women, but healthy ranges also depend on age and individual factors.

Related Tools

More like this: all Health tools, all Calculators tools or the TinySandy home page.