Is the U.S. Navy body fat method accurate?

It is a practical estimate from circumference measurements. It can be useful for consistent trend tracking, but it can be off for individual bodies and should not be treated as a medical measurement.

Why does the calculator ask for neck and waist?

The U.S. Navy method uses height plus circumference differences. Men use neck and waist; women use neck, waist, and hip circumference.

Why is weight optional for the Navy method?

The Navy equation estimates percentage from circumferences. Weight is only needed when you also want estimated fat mass and lean body mass.

Body Fat Calculator

Estimate body fat percentage with the U.S. Navy circumference method or BMI method, with metric and US units plus fat-mass context.

Calculation method

Sex

Units

Height (cm)

Weight (kg) (optional)

Age

Neck (cm)

Waist (cm)

This is an estimate, not a medical measurement. Use the same method over time and treat the result as a trend, not a diagnosis.

Weight is optional for the U.S. Navy percentage; it is only used to estimate fat mass and lean body mass.

Body Fat Percentage Estimate

This calculator follows the English-language search intent for body fat tools: a tape-measure U.S. Navy estimate, an optional BMI-based estimate, and a trend-friendly output that separates percentage, fat mass, and lean mass when weight is provided.

fat mass = weight \times \frac{body fat percent}{100}

Fat mass from body fat percentage.

Estimate, not measurement

Tape and BMI formulas can be convenient for tracking, but they are not equivalent to DEXA, hydrostatic weighing, BodPod, MRI, skinfolds by a trained tester, or clinical assessment.

Choosing A Method

Use the U.S. Navy method when you can measure height, neck, waist, and hip for women.
Use the BMI method only as a rough fallback when you have height, weight, age, and sex.
For progress tracking, keep the same method, tape placement, and time of day.

Frequently Asked Questions

Sources and References

Calculations are based on the listed reference sources. Links open in a new tab.

Updated: June 2, 2026

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