Navy Body Fat Method
The military's tape-measure formula, explained line by line.
The Navy body fat method estimates body fat from circumferences: men use 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76; women use 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387, all in inches. A 34-inch waist, 16-inch neck, 70-inch height gives 15.5 percent for a man; the method typically lands within 3 to 4 points of clinical scans.
Why the Navy trusts a tape
The method was built to screen thousands of service members cheaply and consistently. Waist tracks total fat, neck tracks lean mass, and the log terms fit the relationship found in validation studies against underwater weighing.
It is not the most precise method available, but it is the most practical one you can do at home with a $5 tape.
Measuring like it matters
Waist: around the navel, relaxed, after a normal exhale, tape horizontal. Neck: just below the Adam's apple, looking straight ahead. Hips: widest point, feet together. Height: barefoot, standing tall.
The tape must be snug without denting skin. Take each measurement twice and average; a half-inch error moves the result about a point.
Worked example
Man: waist 34, neck 16, height 70. 86.010 x log10(18) = 108.0; 70.041 x log10(70) = 129.2; 108.0 - 129.2 + 36.76 = 15.5 percent, in the fitness band.
Woman: waist 28, hip 38, neck 13, height 64. 163.205 x log10(53) = 281.4; 97.684 x log10(64) = 176.4; 281.4 - 176.4 - 78.39 = 26.6 percent, in the average band.
Skip the arithmetic
Run the Navy formula on your measurements.
Navy method questions
What is the Navy body fat formula?
For men in inches: 86.010 times log10(waist minus neck), minus 70.041 times log10(height), plus 36.76. For women: 163.205 times log10(waist plus hip minus neck), minus 97.684 times log10(height), minus 78.387.
How accurate is the Navy method?
Validation studies put it within about 3 to 4 points of lab methods for typical bodies. Very muscular or very lean people see bigger gaps, and inconsistent taping adds error on top.
Where exactly do I measure my waist?
The Navy specifies the waist at the navel with the abdomen relaxed after a normal exhale, tape horizontal all the way around. Measuring sucked-in or over clothing inflates or deflates the result.