Vertoq
Body Fat Calculator
Body fat percentage shows how much of your body weight is fat, unlike BMI, which only compares weight to height without distinguishing fat from muscle. This calculator uses the tape-measurement method the US Navy developed, and reports an estimate with a stated margin of error rather than a falsely precise single number.
Measure your waist, neck and, if you're female, hip, add your height and age, and the result is calculated instantly in your browser. No tape measure handy? You can also estimate from height and weight alone, with a wider margin of error.
How to measure your waist
Measure at navel level, tape horizontal, relaxed at the end of a normal exhale.
How to measure your neck
Measure just below the larynx, with the tape sloping slightly downward at the front.
How to measure your hip
Measure at the widest point, feet together.
Rounding to the nearest half centimetre (or quarter inch) is fine — it won’t meaningfully change the result.
Add your weight to also see fat mass and lean mass in the result.
No tape measure? Leave waist, neck and hip blank and we’ll estimate from height, weight and age instead.
How this method works
US Navy tape method
Developed by the US Navy (Hodgdon & Beckett, 1984), this formula estimates body fat percentage from height and the circumference of the waist, neck and, for women, hip. It needs nothing but a tape measure and typically lands within ±3.5 percentage points of a DEXA scan across most body types.
BMI-based estimate
When tape measurements aren’t available, we fall back to a rougher estimate from height, weight, age and sex (the Deurenberg formula). It’s quicker to get but less precise, with a margin of roughly ±5 percentage points, since it can’t account for where on the body the fat actually sits.
Sources: Hodgdon & Beckett (1984), US Navy circumference method; American Council on Exercise body fat reference ranges.
Frequently asked questions
Is body fat percentage better than BMI?
For assessing body composition specifically, yes. BMI only reflects the ratio of weight to height, while body fat percentage shows how much of that weight is actually fat. A muscular, athletic person can register as "overweight" on BMI while having a low body fat percentage.
How accurate is the tape method?
It typically lands within ±3.5 percentage points of a DEXA scan, which is far less accessible. That’s precise enough to track change over time, but it doesn’t replace a clinical measurement.
Can I trust the result if I’m very athletic or older?
With some caution. The formula was fitted on a broader population, so the result can drift further from reality for athletes with unusually low body fat or for older adults whose body composition has shifted.