What is the U.S. Navy Body Fat Calculator?
The U.S. Navy body fat method estimates body fat percentage from simple tape-measure circumference measurements rather than calipers or lab equipment. It was developed by the Naval Health Research Center and is widely used for fitness screening. All measurements are entered in inches.
How to use it
Select your gender, then enter your height, neck and waist measurements in inches. Women also enter a hip measurement. Measure the neck just below the larynx, the waist at the navel for men (or the narrowest point for women), and the hip at the widest point. The calculator returns an estimated body fat percentage and a fitness category.
The formula explained
For men, $$\text{BF}\% = 86.010 \cdot \log_{10}\!\left(\text{waist} - \text{neck}\right) - 70.041 \cdot \log_{10}\!\left(\text{height}\right) + 36.76$$ For women, $$\text{BF}\% = 163.205 \cdot \log_{10}\!\left(\text{waist} + \text{hip} - \text{neck}\right) - 97.684 \cdot \log_{10}\!\left(\text{height}\right) - 78.387$$ The logarithms are base-10 and every length is in inches.
Worked example
A man who is 70 in tall with a 15 in neck and 34 in waist: \(\text{waist} - \text{neck} = 19\). $$\text{BF}\% = 86.010 \cdot \log_{10}(19) - 70.041 \cdot \log_{10}(70) + 36.76 \approx 86.010 \cdot 1.27875 - 70.041 \cdot 1.84510 + 36.76 \approx 17.49\%$$
FAQ
Is this accurate? It is a reasonable estimate (\(\pm 3\text{–}4\%\)) but not as precise as DEXA or hydrostatic weighing.
Why inches? The original Navy regression was calibrated for inches; using centimeters requires a different constant set.
Do I need the hip measurement? Only women use the hip term; for men it is ignored.
