Body Fat Calculator
Estimate your body fat percentage using the U.S. Navy circumference method — just a tape measure needed.
How this calculator works
The U.S. Navy method estimates body fat from circumference measurements using a logarithmic formula, and is a widely used field method that doesn't require calipers or special equipment.
Women use waist + hip − neck in place of waist − neck, with different constants.
Accuracy of this method
The Navy method is reasonably accurate for most people (typically within a few percentage points of DEXA scan results) but can be less reliable for people with very high or very low body fat, or unusual body proportions.
Comparing measurement methods
Besides the Navy circumference method used here, other common body fat estimation methods include skinfold calipers, bioelectrical impedance scales, and DEXA scans. DEXA is generally considered the most accurate but requires specialized equipment, while circumference and caliper methods offer a reasonable free or low-cost alternative.
For tracking progress over time, consistency in measurement method and technique matters more than absolute accuracy — comparing this month's Navy method result to last month's using the same technique is more meaningful than comparing to a one-time DEXA scan result.
A worked example
A man with a 90cm waist, 38cm neck, and 178cm height: using the Navy formula, this works out to roughly 18% body fat, landing in the 'fit' category.
If his waist measured 100cm instead (all else equal), the estimate rises to roughly 24% — illustrating how sensitive this method is to waist measurement specifically, making consistent, careful measurement technique important for tracking change over time.
Comparing measurement methods
Circumference-based methods like the U.S. Navy formula used here are convenient and free, but more precise methods exist: DEXA scans (considered a gold standard), hydrostatic weighing, and bioelectrical impedance scales all offer varying levels of accuracy at increasing cost and complexity.
For most people tracking progress over time, consistency of measurement method matters more than absolute precision — using the same method and technique each time makes trends more meaningful than any single reading. Once you have a body fat estimate, our Lean Body Mass Calculator can break down how much of your weight is fat-free mass.
Frequently asked questions
How accurate is the U.S. Navy body fat method?
It's generally accurate within a few percentage points for most people, making it a solid free alternative to calipers or scans, though not as precise as DEXA or hydrostatic testing.
Why does the formula differ for men and women?
Body fat distribution patterns differ by sex, so the formula includes hip measurement for women to account for typical fat distribution differences.
What is a healthy body fat percentage?
Ranges vary, but roughly 10-20% for men and 18-28% for women are commonly cited as healthy ranges, with athletic ranges running lower — exact healthy ranges vary by age and individual factors.
How often should I re-measure my body fat?
Monthly is a reasonable cadence for tracking meaningful change — body fat percentage doesn't shift dramatically week to week, so frequent measurement mostly captures measurement noise rather than real change.
How does the Navy method compare to a DEXA scan?
DEXA scans are generally considered more accurate, but the Navy circumference method is a reasonably close, free alternative for most people, typically within a few percentage points.
Where exactly should I measure my waist and neck?
Waist is typically measured at the navel level, and neck just below the larynx — consistent placement each time you measure matters more than the exact spot, for tracking change over time.