Body Fat Calculator
Estimate body fat percentage from body measurements using the US Navy method.
28.9%
About this calculator
How This Body Fat Calculator Works
Enter your gender, height, neck, and waist measurements (plus hip measurement for women), and the calculator estimates body fat percentage using the U.S. Navy circumference method.
Worked Example
A woman with height 165 cm, neck 34 cm, waist 80 cm, and hip 95 cm comes out to about 28.9% body fat — in the "Average" range. A man with height 178 cm, neck 38 cm, and waist 90 cm comes out to about 20.1% — also "Average," using the ranges for men.
The Formula
For men: BF% = 495 ÷ [1.0324 − 0.19077×log₁₀(waist − neck) + 0.15456×log₁₀(height)] − 450. For women: BF% = 495 ÷ [1.29579 − 0.35004×log₁₀(waist + hip − neck) + 0.221×log₁₀(height)] − 450. This is the U.S. Navy method, developed to estimate body fat from simple tape-measure circumferences without calipers or specialized equipment.
Accuracy and Limitations
The Navy method is a reasonable field estimate but not as accurate as DEXA scans, hydrostatic weighing, or other lab-based methods — measurement technique matters a lot, since being off by even a centimeter on the waist or neck measurement shifts the result. Measure at the same time of day, without clothing bunching the tape, and hold the tape snug but not compressed for the most consistent readings.
Worked example
At 165cm tall with a 34cm neck, 80cm waist, and 95cm hip, the US Navy formula estimates about 29% body fat — in the "Average" category for women.
Frequently asked questions
How accurate is the US Navy method?
It's a widely used estimate, typically within a few percentage points of more precise methods like DEXA scans, and far more accessible — all it needs is a measuring tape.
Why does the formula need different measurements for men and women?
Men and women tend to store fat differently (waist for men, waist and hip for women on average), so the Navy method uses a different set of measurements and constants for each to stay accurate.
Where exactly should I measure my waist and neck?
Waist: at the narrowest point, usually just above the navel. Neck: just below the larynx (Adam's apple), sloping slightly downward at the front. Keep the tape snug but not compressing the skin.
What do the body fat categories mean?
They're standard ACE ranges — essential fat is the minimum needed for basic health, athletes and fitness ranges reflect regular training, and average/obese reflect typical and elevated ranges respectively. They're general guidelines, not a diagnosis.