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Body Fat Calculator

Estimate body fat percentage from circumference measurements using the US Navy method.

Details

Used for the female formula only.

Your Results

What Body Fat Calculator does

The US Navy method estimates body fat from a few tape measurements: neck and waist for men, plus hips for women, together with height. It was developed as a practical screening tool that needs nothing but a tape measure.

It is far less precise than laboratory methods, but it is repeatable, which makes it useful for tracking change over time even where the absolute number is uncertain.

  • US Navy circumference method
  • Measurements entered in centimetres
  • Result with a broad category

How to use Body Fat Calculator

  1. 1

    Measure carefully

    Use a flexible tape held snug but not compressing the skin. Measure the neck below the larynx, and the waist at the navel for men and at the narrowest point for women.

  2. 2

    Enter your measurements

    All measurements are in centimetres, along with your height.

  3. 3

    Track the trend

    Measure under the same conditions each time. The direction of change is more reliable than any single figure.

Limits and known behaviour

  • Accuracy is limited: comparisons against laboratory methods typically show errors of around three to four percentage points, and larger for individuals with unusual proportions.
  • Results are highly sensitive to measurement technique. A centimetre of difference in where you place the tape changes the answer noticeably, which is why consistency matters more than precision.
  • The method was developed on military populations and is least reliable at the extremes of body composition.
  • It cannot distinguish where fat is stored, which is what carries the metabolic significance.
  • Not appropriate during pregnancy.
  • This is an estimate from a published formula, not a medical assessment. It cannot diagnose anything, and it is no substitute for advice from a clinician who knows your history.

Privacy and data handling

Runs entirely in your browser

  • Every figure you enter stays in this page. Your body measurements is not transmitted, logged or stored anywhere.
  • There is no account, no saved history and no autosave: reloading the page clears the form.

Site-wide data handling, including analytics and advertising, is described in the privacy policy.

Frequently asked questions

How accurate is this compared with a DEXA scan?

Considerably less accurate. DEXA is a reference method; a tape-measure estimate is typically within three to four percentage points and can be further out. Use it for tracking change rather than for an authoritative number.

Why did my result change so much in a week?

Almost certainly measurement variation rather than body composition. Measure at the same time of day, in the same posture, with the tape in the same place, and compare over months rather than weeks.