What The Result Represents
This calculator estimates adult body-fat percentage from height and circumference measurements. It uses separate U.S. Navy equations for men and women because the measurement sets and fitted coefficients differ.
The output is not a direct scan and should not be read as precise to one decimal place, even though a decimal is displayed for consistent tracking.
Equations And Variables
Women: density = 1.29579 - 0.35004 log10(waist + hip - neck) + 0.22100 log10(height)
Body fat % = 495 / density - 450
All equation inputs are centimeters. The tool converts inches before calculation. Log10 means base-10 logarithm.
How To Measure Consistently
- Use a flexible, non-stretch tape on bare skin when practical.
- Stand relaxed, keep the tape level, and avoid compressing the skin.
- Take two or three readings at each site and repeat any pair that differs noticeably.
- For trend tracking, measure at a similar time and under similar conditions.
Worked Example
For a man with a 175 cm height, 80 cm waist, and 38 cm neck, the circumference difference is 42 cm. The equation estimates density at about 1.069, which converts to roughly 12.9% body fat.
Limits And Appropriate Use
The equations were developed from specific military samples and can misestimate people with different body proportions, ages, backgrounds, training histories, or fat distribution. Hydration, breathing, tape tension, and measurement site also affect the result.
Use this tool for adult educational trend tracking. Pregnancy, edema, major weight change, clinical nutrition decisions, and pediatric assessment require a more appropriate professional method.
Frequently Asked Questions
What measurements are required?
Men need height, neck, and waist circumference. Women need height, neck, waist, and hip circumference.
How accurate is the U.S. Navy method?
It is a field estimate derived from circumference measurements and population equations. Individual error can be meaningful, so it is better for repeatable trend tracking than for treating one decimal result as exact.
Should I use metric or imperial units?
Either works as long as every measurement matches the selected system. Imperial entries are converted to centimeters before the equations are applied.
Where should I measure?
Keep the tape horizontal and snug without compressing skin. Measure the neck below the larynx, the waist at the method-specific abdominal site, and for women the hips at the widest point. Repeat each measurement.
Can this replace DEXA or clinical assessment?
No. Circumference equations infer body composition from body shape. They do not directly image fat or lean tissue and may be less suitable when body proportions differ from the development samples.