Body Fat Calculator

Estimate adult body fat using the US Navy circumference method.

Enter your details and select Calculate.

This tool provides an estimate. Verify results before making financial, educational or medical decisions.

Understanding body-fat estimates

This guide explains how to use the calculator, includes an example, discusses limitations and answers common questions.

Circumference-based body-fat formulas offer a rough estimate of body composition without specialist equipment. They are sensitive to measurement technique.

How to use this calculator

Measure the requested body dimensions using a flexible tape, keeping it level and snug but not tight. Enter the units consistently and follow the tool’s measurement labels.

Worked example

If two measurements of the same waist differ by 3 cm, the estimated percentage may change even though actual body composition has not.

When this calculator is useful

Useful for tracking broad changes over time when measurements are taken consistently.

When not to rely on it

The US Navy method is an estimate developed for particular populations. It is not a diagnosis and may be inaccurate for some body types, pregnant people or children.

Practical tip

Measure at a consistent time of day and compare trends rather than treating one decimal place as precise.

Frequently asked questions

Is the result as accurate as a DEXA scan?

No. Tape-based estimates are generally less precise than specialist methods.

Why did my result change overnight?

Tape placement, posture and normal body-size fluctuations can change the estimate.

What should I do with a concerning result?

Discuss it with an appropriate health professional, considering your overall health.

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Educational information only. Results are estimates unless otherwise stated. Verify important financial, medical or legal decisions with a qualified professional.