Body Fat Calculator
Estimate your body fat percentage with a tape measure - height, neck, waist (and hips) - using the U.S. Navy formula.
Enter your age, weight, and tape measurements to see your estimate.
-Body fat · U.S. Navy method
Runs entirely on your device - nothing is ever uploaded.
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How to use the body fat calculator
- Pick US Units or Metric Units, then Male or Female - women add a hips measurement.
- Enter your age and weight, plus height, neck, and waist from a tape measure.
- Read your body fat percentage on the heat scale, with fat mass, lean mass, and a BMI-based second estimate.
How to take the tape measurements
Measure in the morning on bare skin with a flexible tape, level and snug without pressing into the skin, after a normal breath out. Waist goes around the navel for men and at the narrowest point of the midsection for women; neck goes just below the Adam's apple with the tape sloping slightly downward at the front, keeping your neck straight; hips go around the widest point. Take each site twice and average the two readings - a quarter inch either way is normal, so track the trend over weeks rather than one reading.
What the percentage means
Body fat has essential jobs: it cushions organs, insulates the body, stores energy, and produces hormones. Some is vital - roughly 2-5% in men and 10-13% in women - and the commonly cited healthy band is about 8-19% for men and 21-33% for women. Below that, or far above it, is worth a conversation with a clinician. The scale above colors your result from essential through athletic and fit to average and obese, so you can see at a glance where you land.
Two ways the estimate is calculated
The headline number uses the U.S. Navy circumference method, developed from naval health research in the 1980s. It predicts body density from the logarithm of your waist minus neck (plus hips for women) set against the logarithm of your height, then converts density to a fat percentage. All it needs is a tape, which is why the military and many gyms still use it for quick screening.
The table also shows a second estimate from your BMI: roughly 1.2 times BMI plus 0.23 times age, minus about 16 for men and about 5 for women. When the two methods agree, you can be more confident; when they differ, the tape method usually reflects your shape better, because BMI cannot tell muscle from fat. Fat mass is your weight times the percentage, and lean mass is everything else.
This is a screening estimate, not a body-composition test or medical advice. Tape methods are less reliable for children, during pregnancy, and for people whose fat distribution differs from the groups the formulas were built on. For a precise reading, methods such as DEXA, hydrostatic weighing, or bioelectrical impedance are needed.