Body Fat Calculator (US Navy Method)
Estimate body fat percentage from tape measurements. No calipers, no scales — just a tape measure.
How it works
Male: BF% = 86.010·log10(waist − neck) − 70.041·log10(height) + 36.76. Female: BF% = 163.205·log10(waist + hip − neck) − 97.684·log10(height) − 78.387.
How to measure correctly
Neck: below the larynx (Adam's apple), tape horizontal.
Waist: men measure at the navel. Women measure at the narrowest point of the waist.
Hip (women only): at the widest point of the hips.
Measure first thing in the morning, after using the bathroom, before drinking or eating. Stand relaxed, breathe normally, do not suck in or push out.
Why US Navy method?
Originally developed by the US Navy in the 1980s for service personnel screening. Studies show it correlates with hydrostatic weighing (the gold standard) within ±3-4% for most people. Far more accurate than visual estimation, and free unlike DEXA scans.
Body fat categories
The calculator categorises your result against general health guidelines. Essential fat is the minimum needed for normal physiology — going below it is risky. Athletes range is competition-lean. Fitness is visible abs territory. Average is healthy for general population. Obese indicates elevated metabolic risk.
Limitations
Tape methods estimate; they do not measure. Hydration, time of day, recent meals, and body shape all affect the result. The best use is tracking change over time — measure monthly under the same conditions, and look at the trend, not the absolute number.