Estimate adult body fat percentage from height and circumference measurements using the US Navy method.
This tape-measure estimate is not a diagnosis. Hydration, tape position, body shape and measurement technique can affect the result.
How to use the Body Fat Calculator
Select the appropriate measurement formula, then enter weight, height, neck and waist circumference. The female formula also requires hip circumference. Measure on bare skin or light clothing, keep the tape level and repeat each measurement for consistency.
How body fat is estimated
| Result | Method |
|---|---|
| Body fat percentage | US Navy circumference equation |
| Estimated fat mass | Weight × body fat percentage |
| Estimated lean mass | Weight − estimated fat mass |
| Waist-to-height ratio | Waist circumference ÷ height |
How to take measurements
Stand upright without pulling the tape into the skin. Measure the neck below the larynx. Measure the waist consistently at the same anatomical point and after a natural exhale. For the hip measurement, use the widest point. Small tape-position changes can alter the estimate.
Body fat estimate versus BMI
BMI uses only height and weight, while this calculator also uses circumferences. The NHS adult BMI guidance explains that BMI is only one health measure and cannot distinguish muscle from fat. Neither result should be used alone for diagnosis.
Understanding changes over time
For tracking, use the same tape, measurement sites, time of day and conditions. Focus on the longer-term trend instead of small day-to-day differences. Different devices and formulas can produce different percentages.
Related calculators
Compare height and weight with the BMI Calculator. Track alcohol intake with the Alcohol Units Calculator UK. Estimate caffeine intake with the Caffeine Calculator. Browse all tools on the United Kingdom Calculator homepage.
Frequently asked questions
Is this body fat result exact?
No. It is an estimate from circumference measurements and can differ from clinical or laboratory methods.
Why does the female formula require hip circumference?
The selected circumference equation uses hip as well as waist, neck and height measurements.
Can I use inches instead of centimetres?
This calculator accepts centimetres and converts them internally for the equation.
Why did my result change after remeasuring?
Tape position, tension, posture and breathing can change circumference readings.
Is body fat percentage a diagnosis?
No. Use it as a rough tracking measure and discuss health concerns with a qualified professional.