Body Fat Calculator

Estimate your body fat percentage using the U.S. Navy circumference method.

About the Body Fat Calculator

Estimate your body fat percentage from simple tape-measure circumferences, using the U.S. Navy method.

How to use the Body Fat Calculator

Choose US, Metric, or Other units, whichever matches your tape measure.
Select your gender, and enter your age, weight, and height.
Enter your neck and waist circumference (and hip circumference, if female).
Press Calculate to see your estimated body fat percentage, category, and fat/lean mass.

Tips for the Body Fat Calculator

The Navy method is a quick estimate, not as accurate as DEXA scans, hydrostatic weighing, or skinfold calipers — use it to track trends over time rather than as a precise measurement.
Measure your waist at your navel and your neck just below the larynx for the most consistent results.
Age and weight do not directly affect the body fat percentage formula — they are used only to compute fat mass and lean mass.

Formula used by the Body Fat Calculator

For men:
Body Fat % = 495 ÷ (1.0324 − 0.19077×log10(waist − neck) + 0.15456×log10(height)) − 450

For women:
Body Fat % = 495 ÷ (1.29579 − 0.35004×log10(waist + hip − neck) + 0.22100×log10(height)) − 450

where waist, neck, hip, and height are all measured in centimeters.

Example: Body Fat Calculator

A man with an 90 cm waist, 38 cm neck, 178 cm height

Waist: 90 cm
Neck: 38 cm
Height: 178 cm

Result: Body fat ≈ 20.1% — "Acceptable" category (fat mass ≈ 16.1 kg on an 80 kg body)

Plugging waist − neck = 52 cm and height = 178 cm into the Navy formula gives 495 ÷ 1.0529 − 450 ≈ 20.1%, which the tool classifies as "Acceptable" for men.