Body Fat Calculator
The US Navy tape-measure method, with its accuracy stated honestly.
About this calculator
The US Navy circumference method estimates body fat from a tape measure: height, neck and waist (plus hips for women), fed through a formula the Navy validated against underwater weighing. Enter the measurements in centimetres, get a percentage and where it sits in the ACE category bands.
Measuring right, and what to expect
Technique decides the result: measure the waist at the navel (women: at the narrowest point, hips at the widest), the neck just below the larynx, tape snug but not compressing, and measure at the same time of day each time. Honest accuracy: for most bodies the estimate lands within ยฑ3โ4% of a DEXA scan โ good enough to be useful, wide enough that chasing single points is noise. Very muscular and very lean builds read least accurately. The real value is the trend: measured the same way monthly, the direction of change is trustworthy even when the absolute number is approximate โ the same philosophy as BMI (honestly assessed here), which knows your weight but nothing about what it's made of. This is arithmetic, not diagnosis; body-composition decisions worth medicating or training hard for deserve a professional's measurement.
Frequently asked questions
How accurate is the Navy body fat method?
Typically within ยฑ3-4 percentage points of a lab DEXA scan when measured carefully โ least accurate for very muscular or very lean builds. The month-to-month trend is more trustworthy than any single reading.
Where exactly do I measure?
Neck just below the larynx; waist at the navel for men, narrowest point for women; hips (women) at the widest point. Tape level and snug, not digging in โ and repeat at the same time of day.
What's a healthy body fat percentage?
By the ACE bands: fitness sits around 14-17% for men and 21-24% for women, with 'average' extending to 25% and 32% respectively. Essential fat โ the floor the body needs โ is about 3-5% for men and 10-13% for women.
Why does it differ from my smart scale?
Bioimpedance scales estimate from an electrical signal that shifts with hydration, food and warm feet โ swings of several points in a day are normal. Neither method is a lab; pick one, keep conditions constant, watch the trend.