Body fat
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Body Fat Percentage Estimator (US Navy Method)
US Navy tape estimate from sex, height, waist, neck, and hip (women) in inches.
Page updated 2026-09-04.
Calculator
Calculated Results
Circumference measurements, not a scan
For a male at 70 inches tall with a 34-inch waist and 15.5-inch neck, the Navy method estimates 16.52% body fat, using the male-specific version of the formula (which doesn't require a hip measurement).
The Navy method uses waist and neck circumference (plus height) for men, and additionally requires a hip measurement for women -- this asymmetry exists because the formula was empirically derived to correlate with body fat differently by sex, reflecting typical differences in fat distribution patterns between men and women.
This is a tape-measurement-based estimate, not a direct measurement of actual body fat -- it works by correlating simple circumference measurements (which are easy for anyone to take with a measuring tape) against body fat percentages validated in the original Navy research population.
Why this estimate has meaningful error bars
Tape estimate, not DEXA. Hip is used for women only. Compared to a gold-standard method like DEXA scanning (which directly measures bone, fat, and lean tissue via X-ray absorption), tape-based methods like this one carry a wider margin of error -- commonly cited as several percentage points in either direction, which matters if you're tracking small changes over time rather than a single rough snapshot.
Measurement technique matters significantly for accuracy -- the waist measurement specifically needs to be taken at a consistent, correctly specified location (often at the navel or the narrowest point, depending on the exact protocol version) and a measurement taken inconsistently between two check-ins can show a change that's actually just measurement noise, not a real body composition change.
This formula was developed and validated primarily on a military population -- its accuracy may vary somewhat outside that specific demographic, which is a known limitation of anthropometric formulas built from a specific reference population.
Related body-composition tools
Once you have a body fat percentage (from this or another method), the Lean Body Mass Calculator converts that percentage into actual pounds of lean versus fat mass.
For a simpler height-and-weight-only estimate (with its own different set of limitations), the BMI (Body Mass Index) Calculator is a related but distinct measure.
Frequently Asked Questions (FAQ)
Why doesn't the male formula use a hip measurement?
Tape estimate, not DEXA. Hip is used for women only. The Navy method's formula was empirically derived separately for men and women, based on how circumference measurements correlate with actual body fat in each sex. For men, waist and neck (with height) were found sufficient; for women, hip circumference is additionally needed.
How accurate is this compared to a DEXA scan?
Tape estimate, not DEXA. Hip is used for women only. Less precise -- tape-based methods like this typically carry an error margin of several percentage points compared to DEXA, which directly measures body composition via X-ray absorption rather than estimating it from circumference correlations.
Does where exactly I measure my waist matter for accuracy?
Yes, significantly. The waist measurement needs to be taken at a consistent, correctly specified location according to the method's protocol. Inconsistent measurement location between check-ins can produce an apparent change in body fat that's actually just measurement inconsistency, not a real change.
Was this formula validated on a general population?
It was developed and validated primarily using a military population, which is a known limitation -- its accuracy for people outside that specific demographic (in body type, age range, or fitness level) may vary somewhat from what the original research supports.
Should I use this to track small body fat changes week to week?
It's better suited to tracking broader trends over longer periods than precise week-to-week changes, given the method's inherent margin of error -- small week-to-week fluctuations could easily be measurement noise rather than a real body composition change.
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