How this Navy-method body fat calculator works
The equations use base-10 logarithms of height and selected circumferences in inches. Weight is not used to estimate the percentage; it is used afterward to estimate fat mass and lean body mass.
Male %BF = 86.010 × log10(abdomen − neck) − 70.041 × log10(height) + 36.76Female %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387lean mass = body weight × (1 − body-fat percentage)Understanding your results
A circumference result is an estimate, not a precise measurement. Repeat under consistent conditions, keep the tape level and snug without compressing skin, and use the same landmarks. Trends measured consistently may be more informative than a single value.
Why BMI can mislead muscular athletes
BMI uses only height and weight, so it cannot distinguish muscle, bone, and fat. That limitation matters for bodybuilders. The Navy method adds body-shape information, but unusual muscularity and fat distribution can still reduce accuracy.
Frequently asked questions about bodybuilder body fat
How accurate is the U.S. Navy body fat method?
Published military research describes errors of several body-fat percentage points relative to laboratory methods. Individual error may be larger because of tape placement, observer technique, hydration, body proportions, and muscularity. Treat the result as a repeatable field estimate, not an exact composition measurement.
Where should bodybuilders measure the waist?
For the male equation, military protocols use an abdominal circumference at the navel. The female equation uses a natural-waist circumference plus hips at the greatest protrusion. Keep the tape horizontal and follow one protocol consistently across measurements.
Is lean body mass the same as muscle mass?
No. Lean body mass includes muscle, bone, organs, water, connective tissue, and other non-fat components. Subtracting estimated fat mass from body weight does not isolate skeletal muscle and should not be presented as a muscle measurement.