Body Fat Percentage Calculator
Enter a few tape-measure circumferences to estimate your body fat percentage using the US Navy method.
Fill in the form and hit calculate to see your results here.
Your estimated body fat
—Circumference methods are an estimate — for precise tracking, use the same tape and technique each time and watch the trend.
How the US Navy method works
It uses the relationship between waist, neck (and hip, for women) circumference relative to height to estimate body fat — no calipers or scans needed, just a tape measure.
Getting an accurate measurement
Measure first thing in the morning, keep the tape snug but not compressing the skin, and take each measurement two or three times to make sure they're consistent.
How accurate is it?
It's generally within a few percentage points of more precise methods like DEXA scans for most people — a solid free option, best used to track trend over time rather than one precise number.
The formula
# US Navy method (imperial units, inches)
Men:
%BF = 86.010 × log10(waist - neck) - 70.041 × log10(height) + 36.76
Women:
%BF = 163.205 × log10(waist + hip - neck) - 97.684 × log10(height) - 78.387
Metric measurements are converted to inches internally before applying the formula, then converted back for display.
Common questions
Body fat distribution differs by sex on average, so the Navy method uses separate formulas — women's also factors in hip measurement, men's doesn't need it.
Not quite — DEXA and other imaging methods are more precise. This method is a solid free estimate, especially useful for tracking change over time rather than a single absolute number.
At the navel, standing relaxed, without pulling the tape tight enough to compress the skin. Measuring at the same spot each time matters more than the exact anatomical location.
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