Body Fat Calculator
Estimate your body fat percentage using the U.S. Navy circumference method. Metric or imperial, no scale required.
Last reviewed
The Body Fat Calculator estimates your body fat percentage from four tape-measure circumferences using the U.S. Navy method. It's calculated as BF% = 495 / (density) - 450, where density is derived from your waist, neck, height, and (for women) hip measurements. No scale or calipers required.
Body Fat Percentage
16.9%
Acceptable Range (ACE)
18-24%
Height Context
5'9"
Measurements
Strategy Note
Body fat percentage is a better composition signal than BMI alone. Pair it with a waist-to-hip ratio check to see how that fat is distributed.
Check WHRComposition Status
ACE Classification Gauge
Fitness
A lean, visibly fit range for a generally active adult.
The Science of the U.S. Navy Circumference Method
The formula was developed by Hodgdon and Beckett at the Naval Health Research Center in 1984 as a fast, equipment-free alternative to hydrostatic (underwater) weighing. It estimates body density from simple tape-measure circumferences, then converts that density to a fat percentage using the Siri equation (the same conversion step used by most skinfold and bioimpedance methods).
Category bands above follow the American Council on Exercise (ACE) body fat norms, and the underlying formula and its validation are documented in the National Academies Press review of body composition standards used across the U.S. military services.
How to measure each input. Use a flexible tape measure, snug but not compressing the skin. Neck: just below the larynx (Adam's apple), tape sloped slightly downward at the front. Waist: at the navel, at the end of a normal exhale. Hip (women only): around the widest part of the buttocks. Measure standing, and take the average of two readings for each site.
Worked example. A man 175 cm tall with an 85 cm waist and 38 cm neck: density = 1.0324 − 0.19077 × log₁₀(85−38) + 0.15456 × log₁₀(175) ≈ 1.0601, giving BF% = 495 ÷ 1.0601 − 450 ≈ 16.9% (matching this calculator's default inputs above and landing in the "Fitness" band).
The Hodgdon-Beckett Formula
Men
Women
w = waist, n = neck, h = height, p = hip (women only). All measured in centimeters. log = log10
Limitations. This tape-measure method is accurate to within roughly 3-4 percentage points of hydrostatic weighing for most adults. It's good for tracking trends, not a clinical-grade body composition scan. It's an estimate, not a diagnosis; talk to a clinician if you have concerns about your body composition.
Clinical Inquiries
?Why does the Navy method need a neck measurement?
Neck circumference is used as a low-fat reference point. Subtracting it from the waist (and hip, for women) isolates the portion of abdominal girth that scales with body fat rather than skeletal frame.
?How accurate is the U.S. Navy circumference method?
In the original Hodgdon and Beckett (1984) validation against hydrostatic (underwater) weighing, the method was accurate to within roughly 3-4 percentage points for most adults. It's precise enough for tracking trends, though not a clinical-grade measurement.
?Why are there separate formulas for men and women?
Men and women store fat differently, and women carry a higher percentage of essential fat. The formula accounts for this by adding hip circumference and using different coefficients for the female equation.
About this calculator. Results are estimates for education and planning, based on the inputs you enter and the published formula described above. Everything runs in your browser; nothing you type is sent to us or stored. It is not financial, tax, legal or medical advice. Read the disclaimer and our methodology.
Spotted an error or an out-of-date figure? Tell us and we will correct it and note the change in the update log.