How the Navy method works
The US Navy circumference method was developed by Hodgdon and Beckett at the Naval Health Research Center in the 1980s as a fast way to estimate body fat without lab equipment. It uses the fact that waist circumference rises with abdominal fat while neck circumference tracks frame and muscle. The male equation (measurements in cm) is:
Body fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
Variants of this circumference approach are still used for military body-composition standards today.
How to measure for an accurate result
Small measuring errors move the result a lot, so take each measurement two or three times and average them.
- Waist: horizontally at the level of your navel, relaxed (don’t suck in), at the end of a normal exhale.
- Neck: just below the larynx (Adam’s apple), with the tape sloping slightly down toward the front.
- Height: barefoot, standing straight against a wall.
- Measure at the same time of day — first thing in the morning is most consistent.
Reading your result
The calculator places your result in general ranges for adult men: essential fat (2–5%), athletic (6–13%), fitness (14–17%), average (18–24%), and above average (25%+). Like every field method, the Navy formula is an estimate. It tends to be reasonable for most men but can be off by several percentage points compared with DXA scans, especially for very lean, very muscular, or high-body-fat individuals. The most useful thing it gives you is a trend — the same tape, the same technique, measured every few weeks.
Frequently asked questions
How accurate is the Navy body fat calculator?
It is typically within a few percentage points of lab methods for average builds, with larger errors at the extremes. It is best used to track change over time with consistent measuring technique.
Where do I measure my waist for the Navy method?
For men, measure horizontally around the abdomen at the level of the navel, relaxed, at the end of a normal breath out.
What is a healthy body fat percentage for a man over 40?
Ranges of roughly 14–24% are common for healthy adult men, with the fitness range around 14–17%. Waist size and trends matter more than hitting a single number.
Why does this calculator only use the male formula?
The female Navy equation also requires a hip measurement. The site is focused on men, so the current version implements the male formula only.