Body Fat Calculator: Estimate Body Fat Percentage With a Tape Measure
Enter your height and a few tape measurements to estimate body fat percentage with the U.S. Navy circumference method, in inches or centimeters.
The Navy method estimates body fat from a log formula of your neck, waist and height, plus hips for the female equation. A man 70 inches tall with a 15-inch neck and a 34-inch waist comes out at about 17.5% body fat; at 180 pounds that is roughly 31.5 pounds of fat and 148.5 pounds of everything else. Treat it as an estimate that can miss by several points.
This calculator gives a rough estimate for general education only. It is not medical advice, a diagnosis or a substitute for a professional assessment. Tape measurement equations can differ from lab methods by several percentage points, and they are less reliable for very muscular people, during pregnancy and for anyone under 18. The result says nothing about your health on its own. If you are concerned about your weight, body composition or eating, talk to a doctor or another qualified health professional.
Estimated body fat
17.5%
A tape-measure estimate, not a lab measurement. For any one person it can land several percentage points above or below a lab result.
- Fat mass
- 31.5 lb
- Everything else (lean mass)
- 148.5 lb
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About the Body Fat Calculator
This calculator uses circumference equations from 1984 U.S. Navy research to estimate body fat without calipers or a scan. The armed services have since changed how they screen body composition, so this is not the current military standard, just a long-used tape method. The male equation uses the waist at the navel minus the neck, against height. The female equation adds the hips at their widest point and measures the waist where it is smallest. Both take the logarithm of those lengths, so a half inch at the waist moves the answer more than you might expect, which is why careful measuring matters: keep the tape level and snug without pressing into the skin, measure the neck just below the Adam's apple, take each reading two or three times, and use the average. If you enter your weight, the page also splits it into fat mass and everything else, which is the easier number to track over months. The estimate works best for watching your own trend with the same tape and the same technique. It is less reliable for very muscular builds, during pregnancy, and for anyone under 18, and it is not a measure of health on its own.
Frequently asked questions
How accurate is the Navy body fat method?+
It is a rough estimate. For a given person it can land several percentage points above or below a lab method such as a DEXA scan or underwater weighing, and the error grows when the tape is placed differently from one day to the next. It is more useful for tracking change than for a single exact figure.
Where do I measure my waist and neck?+
Measure the neck just below the Adam's apple with the tape angled slightly down toward the front. For the male equation, measure the waist level with the navel after a normal breath out. For the female equation, measure the waist at its narrowest point and the hips at the widest part of the buttocks.
Why does the calculator ask which formula to use?+
The 1984 work produced one equation for men and a different one for women, with hip measurement only in the female version. Pick the one that matches the body you are measuring. The two equations were fit on different groups, so their results are not interchangeable.
Can I use centimeters?+
Yes. Switch the units to centimeters and kilograms. The calculator converts each length to inches, at exactly 2.54 centimeters per inch, before applying the formula, so the result is the same either way.
What body fat percentage should I aim for?+
This page does not set a target. Healthy body composition depends on age, sex, genetics, sport and health history, and a single tape estimate is too rough to judge against a cutoff. If you have a goal in mind, a doctor or registered dietitian can help you set one that fits you.
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