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Body Fat Calculator

Enter your height and a few tape-measure circumferences to estimate body-fat percentage with the US Navy circumference method. The formula and every value it uses are shown. It is an estimate for adults only — not a diagnosis — and it runs entirely in your browser.

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1. Measurements

US Navy method · adults

Measure with a flexible tape, snug but not tight. Men: waist at the navel. Women: waist at the narrowest point, hips at the widest point.

2. Estimate

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Enter your measurements, then press Estimate body fat.
Estimate only. The US Navy method approximates body fat from a few measurements, and measuring technique strongly affects the result. It is not a medical measurement or diagnosis and does not assess health risks. Speak to a qualified healthcare professional for personal advice.
About this tool

About Body Fat Calculator

Body Fat Calculator estimates adult body-fat percentage using the US Navy circumference method, from height and neck and waist measurements — plus hip circumference for women. It shows the result, the exact formula and each intermediate value, in centimetres or inches.

The circumference method needs only a tape measure, making it a convenient way to estimate body composition over time. Showing the formula and steps makes clear how the number is produced and how sensitive it is to measurement.

How to use

Step by step

  1. Choose the sex used by the formula and the measurement unit.
  2. Measure and enter your height.
  3. Measure and enter your neck and waist circumference.
  4. Women: also measure and enter hip circumference.
  5. Press Estimate body fat, then review the calculation and copy or download the summary.
Key features

What it offers

  • US Navy (Hodgdon & Beckett) circumference method for men and women
  • Centimetre or inch measurements
  • Formula, body density and every intermediate value shown
  • Hip circumference required for the female equation — never assumed
  • Rejects impossible measurements and formula-invalid combinations
  • No disease-risk labels or medical interpretation
Best practices

Tips for best results

  • Measure at the same time of day, relaxed, before eating or exercise.
  • Keep the tape level and snug without compressing the skin.
  • Take two or three readings and use the average.
  • Track the trend over time rather than relying on a single result.
Benefits

Why people use it

Tape-measure simple

No special equipment needed.

Transparent

Formula and steps are shown.

Careful validation

Missing or impossible values are flagged.

Private

Measurements stay in your browser.

FAQ

Common questions

A method developed by Hodgdon and Beckett for the US Navy (1984) that estimates body density — and from it body-fat percentage — using height and circumference measurements: neck and waist for men, and neck, waist and hip for women.
With all measurements in centimetres: men — %BF = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450; women — %BF = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. Inch measurements are converted to centimetres (× 2.54) first.
Use a flexible tape, snug but not compressing the skin. Neck: just below the larynx. Waist: men at the navel, women at the narrowest point. Hip (women): at the widest point of the buttocks. Measure relaxed, not after a meal or exercise, and take the average of a few readings.
The method uses different equations for men and women, and only the women’s equation includes the hip. The calculator requires it for the female calculation rather than guessing.
It is an approximation. Results depend heavily on measuring technique and can differ by several percentage points from methods such as DEXA scans. It is not a medical measurement or diagnosis, and it does not assess health risks.
The method needs the waist to be larger than the neck (for women, waist + hip larger than neck), and every value must be in a realistic adult range. Results outside 2–70% usually mean a measuring or unit mistake, so they are rejected instead of shown.
No. Everything is calculated in your browser and nothing is stored.

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Private by design

This runs entirely in your browser

No file or text you enter here is uploaded. Encoding and decoding happen on your device using native browser APIs — close the tab and nothing remains on a server.

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