Body Fat Calculator
Estimate body fat with the U.S. Navy method.
cm or in
cm or in
cm or in
cm or in — required for females
Results update as you type.
This calculator provides estimates based on population research. Results are not medical advice. Consult a qualified healthcare provider before making health or nutrition decisions.
How it works
Body fat percentage is the share of your total body weight that is fat tissue, as opposed to muscle, bone, organs and water. It is a more meaningful gauge of composition than weight or BMI alone, because two people at the same weight can carry very different amounts of fat and lean mass. This body fat calculator uses the U.S. Navy circumference method, developed by Hodgdon and Beckett in 1984, which the Navy adopted to screen personnel without expensive equipment. It estimates fat from tape measurements: neck and waist for men, plus hip for women, all read against height. Researchers derived the equations by regressing these girths against body density measured by underwater weighing, so the tape figures stand in for the harder laboratory test. That is the appeal of a body fat calculator built on this method: it needs only a tape measure yet lands within a few percentage points of a gold-standard scan for average builds. Athletes, military recruits, coaches and anyone tracking a fat-loss or recomposition programme use a body fat calculator to monitor progress that the bathroom scale hides. Laboratory methods such as DEXA and hydrostatic weighing remain more precise, so treat this estimate as a tool for tracking change over time rather than a clinical diagnosis. Measure snugly without compressing the skin.
U.S. Navy circumference method using log10 of neck, waist (and hip for women)
The method exploits the fact that fat accumulates at the waist and hips while the neck stays comparatively lean. The gap between waist (and hip) girth and neck girth therefore tracks how much fat a person carries, and dividing by height normalises for body size. Logarithms linearise the relationship that the researchers found between these circumferences and body density measured underwater.
Source:U.S. Navy body composition method (Hodgdon & Beckett, 1984)
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter sex, height, neck and waist.
- 2
Adjust the options
Adjust units and hip (female only) if they apply — sensible defaults are already set.
- 3
Read your result
Body fat updates instantly as you type — no button to press.
Frequently asked questions
How accurate is the Navy body fat method?
For average body types it typically lands within three to four percentage points of a DEXA or hydrostatic scan, which is impressive for a tape measure. Accuracy slips for very lean athletes and for people carrying fat in unusual patterns, because the formula assumes a standard distribution. Its real strength is consistency: measured the same way each time, it tracks change reliably even when the absolute number is slightly off.
What is a healthy body fat percentage for men and women?
Women naturally carry more essential fat, so healthy ranges differ by sex. A common guide puts men's fitness range near 14 to 24 percent and women's near 21 to 31 percent, with athletes lower. Essential fat sits around 3 percent for men and 12 percent for women, below which health suffers. These are general bands, not targets everyone should chase.
Where exactly do I measure the waist and neck?
Measure the neck just below the larynx with the tape sloping slightly downward at the front. For the waist, men measure at the navel and women at the narrowest point of the torso. Keep the tape level all the way around and snug against the skin without squeezing. Measure on bare skin, after exhaling normally, for the most repeatable readings.
Why do women need to measure their hips?
Women typically store more fat around the hips and thighs than men do, so waist and neck alone would understate their body fat. Adding hip circumference gives the female equation a second site that reflects this distribution, which is what keeps the estimate accurate. The male formula omits it because men store proportionally more fat around the abdomen, already captured by the waist measurement.
How often should I recheck my body fat?
Every two to four weeks is enough to see a real trend, since body composition changes slowly. Measuring more often mostly captures day-to-day noise from hydration, food and salt. For the cleanest comparison, measure at the same time of day, ideally in the morning before eating, and use the same tape and technique each time so the numbers stay directly comparable.