Both of these calculators estimate body fat percentage from tape measurements, but they use different measurement sets, different equations, and different outputs. The Army body fat calculator applies a weight-and-waist circumference method with age-band pass or fail limits. The body fat calculator applies the legacy Hodgdon circumference coefficient set to neck, waist, and hip measurements and derives fat and lean mass. Each page points to the other as the alternative: the body fat page sends official Army tasks to the Army calculator, and the Army page lists the legacy circumference estimate as a companion screen.
What each calculator does
The Army body fat calculator takes sex, age, body weight in pounds, and waist circumference entered as feet plus inches (the inches field runs 0 through 11 with half-inch increments). For males the raw estimate is −26.97 − 0.12 × weight + 1.99 × waist; for females it is −9.15 − 0.015 × weight + 1.27 × waist. The result is rounded to the nearest whole percent and compared with an age- and sex-based maximum: male limits of 20, 22, 24, and 26 percent and female limits of 30, 32, 34, and 36 percent across the under-21, 21–27, 28–39, and 40-and-up bands, producing an unofficial pass or fail. The page stresses that the equation uses weight and waist only — no height, neck, hip, or body composition — and that a one-inch waist difference shifts the male result by 1.99 percentage points before rounding.
The body fat calculator takes imperial or metric measurements: height, weight, neck, waist, and — for the female equation — hip. It applies the legacy coefficient set, with the male equation 495 / (1.0324 − 0.19077·log10(W − N) + 0.15456·log10(H)) − 450 and the female equation 495 / (1.29579 − 0.35004·log10(W + Hip − N) + 0.221·log10(H)) − 450, where W is waist, N is neck, and H is height. The percentage displays to one decimal, and the page derives estimated fat mass (weight × percentage ÷ 100) and lean mass (weight − fat mass). For the starting male example of 70 in height, 180 lb, a 15 in neck, and a 34 in waist, the estimate is 11.1% with 19.9 lb of fat mass and 160.1 lb of lean mass. Validation requires all measurements positive, waist greater than neck for males, and waist plus hip greater than neck for females. The page assigns no health, fitness, or military-compliance category.
Side-by-side
| Army body fat calculator | Body fat calculator (circumference method) | |
|---|---|---|
| Measurements | Sex, age, weight, waist (feet + inches) | Sex, height, weight, neck, waist, and hip (female) |
| Male equation | −26.97 − 0.12 × weight + 1.99 × waist | 495 / (1.0324 − 0.19077·log10(W − N) + 0.15456·log10(H)) − 450 |
| Female equation | −9.15 − 0.015 × weight + 1.27 × waist | 495 / (1.29579 − 0.35004·log10(W + Hip − N) + 0.221·log10(H)) − 450 |
| Display | Nearest whole percent | One decimal place |
| Extra outputs | Unofficial pass/fail against age-band limits | Estimated fat mass and lean mass |
| Category assigned | Unofficial Army-style screening comparison | None — no health, fitness, or military category |
When to use which
Use the Army body fat calculator when you want an Army-style body-composition screening check: the page pairs the estimate with the AR 600-9 age bands and gives an unofficial pass or fail against a 20–36 percent limit grid. Its measurement set is minimal — weight and waist — which makes it quick but also sensitive: the same 34-inch waist example that yields a different percentage here than on the other page is expected because the equations are different.
Use the body fat calculator when you want a fuller circumference picture: it asks for neck, waist, and hip (plus height), shows the estimate to one decimal, and derives fat mass and lean mass so you can see how the percentage maps onto body weight. Its legacy Hodgdon equations are the coefficient set the U.S. military adopted in 2002, but the page deliberately does not attach a compliance or health category. Pair either estimate with the BMI calculator for a weight-and-height screening context, as both pages suggest.
Limits and disclaimer
Both pages are educational only and are not medical advice, and neither makes an official military determination. Circumference equations estimate body fat from body-size patterns; they do not measure fat mass directly like a laboratory method. Tape placement, tension, posture, hydration, and recent meals can shift either estimate, and the Army page calls out that small waist differences move the male formula by 1.99 percentage points per inch before rounding. The body fat page notes that derived fat and lean masses inherit the same uncertainty. For medical questions consult a qualified clinician; for Army compliance questions use current official Army Body Composition Program materials and authorized personnel.