Body Fat Percentage Calculator

How the Navy body fat method works

This calculator uses the US Navy circumference method, developed by researchers Hodgdon and Beckett at the Naval Health Research Center in 1984. Instead of pinching skinfolds with calipers or stepping into a dunk tank, it estimates body fat from a handful of circumference measurements and your height, run through a regression formula built from a large sample of Navy personnel.

The method was validated against hydrostatic (underwater) weighing, which was the reference standard at the time. For men, the formula’s predictions correlated with underwater-weighing results at 0.90, a strong correlation. For women, it was 0.85, still solid but a bit less precise, mainly because fat distribution patterns are harder to capture from torso measurements alone in women than in men.

There’s also an inch-based version that skips the density step and spits out a percentage directly, which is what the calculator switches to when you select inches. Both versions come from the same original research and give matching results for the same measurements.

An honest limit worth knowing

The Navy method has a documented bias: it tends to underestimate body fat at the higher end of the range and overestimate it at the lower end. This isn’t a flaw nobody noticed. The Navy’s own later research flagged it directly, and the method was still kept in service because the error runs in a safer direction for military screening purposes. For your own tracking, it means two things: don’t expect pinpoint accuracy if you’re very lean or carrying significantly more fat than average, and don’t panic over a few points of difference between the Navy method and a different method like a DEXA scan or a skinfold test. The published standard error of the estimate is roughly 3 to 4 percentage points either way.

How to measure correctly

Accuracy here depends entirely on measurement technique, more than almost any other calculator on this site. A tape pulled too tight or placed an inch off can swing your result by several percentage points.

• Neck: measure just below the larynx (Adam’s apple), tape sloping slightly downward at the front.
• Waist (men): at the navel, or the narrowest point above the hip bones.
• Waist (women): at the narrowest point of the torso, usually above the belly button.
• Hip (women only): at the widest part of the hips and glutes.
• Keep the tape snug against the skin without compressing it, measure standing upright, and take each measurement twice to confirm consistency.

What the result categories mean

The calculator sorts your result into one of five bands, based on classification ranges commonly used by the American Council on Exercise:

Essential fat is the minimum needed for basic physiological function. Nobody should be trying to sit at or below that number through diet alone, and doing so for an extended period carries real health risk.

How this compares to other methods

Our honest take: the Navy method is the best free, at-home option that doesn’t depend on tester skill the way calipers do, and it doesn’t swing around with your hydration the way a bathroom BIA scale does. It won’t match a DEXA scan exactly, and it was never meant to.