Body Fat Calculator — Navy Method Body Fat Calculator
The tape-measure view: the U.S. Navy circumference method estimates body fat percentage from height, neck, and waist (plus hip for women) using the logarithmic equations Hodgdon and Beckett published at the Naval Health Research Center in 1984. A 72-inch man with a 16-inch neck and 36-inch waist screens at 18.6%; measurement technique is what makes or breaks the result, so this page covers exactly where the tape goes. Within roughly ±3–4 points of DEXA, it is a screening estimate for tracking trends, not a clinical measurement.
Body fat estimate
Estimated body fat
17.5%
Fitness (ACE range)
Method
U.S. Navy circumference method (Hodgdon & Beckett, 1984), computed from height, neck, and waist.
Screening estimate, not a medical measurement — the Navy method typically runs within ±3–4 points of a DEXA scan.
Both methods are screening estimates computed in your browser from the numbers you enter. They do not measure body composition directly and are not a diagnosis or medical advice — consult a healthcare professional before acting on the result.
Where the tape goes, exactly
The Navy equations were calibrated against specific anatomical sites, so precision about placement matters more than precision about the decimal. Neck: immediately below the larynx, tape sloping slightly down toward the front, shoulders down and relaxed — shrugging tightens the trapezius and inflates the reading. Men's waist: level with the navel, arms at the sides, at the end of a normal exhale. Women's waist: the narrowest visible point of the torso. Women's hip: the widest point around the buttocks, feet together.
Keep the tape horizontal, snug but never compressing the skin, and repeat each site two or three times until readings agree within a quarter inch. Small tape errors move the result meaningfully: at 70 inches of height and a 15-inch neck, a waist of 34 inches returns 17.5%, so half an inch of slack or compression on one site can shift the estimate by roughly a point. Measuring at a consistent time of day — morning, before eating, is the usual choice — removes the daily waist swing from your trend line.
A standard built for military screening
Hodgdon and Beckett developed the equations in 1984 at the Naval Health Research Center in San Diego so the Navy could screen body composition at scale with nothing but a tape measure — no calipers, no technician training, no lab. Variants of the circumference method remain the basis of body-composition assessments across the U.S. military, which is why it is often simply called the "Navy method" or "tape test."
That heritage explains both its strengths and its limits. It was designed to be repeatable across thousands of people and forgiving of equipment, not to be exact for any individual — service members flagged by the tape are typically referred to more precise testing rather than judged on the tape alone. Used the same way here, as a consistent screen that points to whether a closer look is worth it, it does exactly what it was built for.
Questions
- What body fat does the Navy method give a 72-inch man with a 16-inch neck and 36-inch waist?
- 18.6%. The male equation is 86.010 × log10(36 − 16) − 70.041 × log10(72) + 36.76, every measurement in inches. As with all tape estimates, read it with a roughly ±3–4 point band around it.
- Why does the women's equation need a hip measurement?
- Women's fat distribution carries proportionally more mass at the hips, so the 1984 calibration found waist alone insufficient. The female equation uses waist + hip − neck inside the logarithm, and without a positive hip entry the calculator reports no estimate rather than guessing.
- Is this the same calculation the military uses?
- It uses the same published Hodgdon–Beckett circumference equations that underpin military tape tests, but it is not an official assessment — services periodically adjust their procedures, sites, and standards, and an official measurement is taken by trained personnel. Treat this page as a screening estimate, not a fitness determination.