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 the AR 600-9 circumference equations to height, neck, waist, and (for the female equation) hip, showing the age-band screening-table maxima as reference without a pass or fail verdict. 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, height in inches, neck in inches, waist in inches, and — for the female equation — hip in inches, all to the nearest half inch. For males the raw estimate is 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76; for females it is 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387. The result is rounded to the nearest whole percent, and the page shows the AR 600-9 Table B-2 age-band screening-table maxima (male 20, 22, 24, and 26 percent and female 30, 32, 34, and 36 percent across the under-21, 21–27, 28–39, and 40-and-over bands) as reference only — it emits no pass or fail verdict. The male waist is the abdomen at navel level, and the page stresses measurement procedure: tape placement, posture, and the log10 base all affect the estimate.
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, height, neck, waist, hip (female), in inches | Sex, height, weight, neck, waist, and hip (female) |
| Male equation | 86.010·log10(waist − neck) − 70.041·log10(height) + 36.76 | 495 / (1.0324 − 0.19077·log10(W − N) + 0.15456·log10(H)) − 450 |
| Female equation | 163.205·log10(waist + hip − neck) − 97.684·log10(height) − 78.387 | 495 / (1.29579 − 0.35004·log10(W + Hip − N) + 0.221·log10(H)) − 450 |
| Display | Nearest whole percent | One decimal place |
| Extra outputs | Age-band screening maxima (reference only) | Estimated fat mass and lean mass |
| Category assigned | None — no pass/fail, educational reference | None — no health, fitness, or military category |
When to use which
Use the Army body fat calculator when you want the AR 600-9 circumference estimate with the age-band screening-table maxima shown for context: the page pairs the whole-percent estimate with the four reference bands but deliberately does not pass or fail you against them. Its measurement set — height, neck, waist, and hip for women — follows the regulation’s sites, and the estimate is sensitive to measurement care: around typical measurements a one-inch waist difference moves the male log10 term by about two percentage points.
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 estimate through the log10 term — around typical measurements, roughly two percentage points per inch for the male equation and about 1.3 points for the female equation. 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.