Body Fat Calculator
A tape measure and three numbers — no equipment, no cost, ±3% of a DEXA scan.
Read the maths behind this tool: BMI Formula: What the Number Means and Where It Fails
Why circumference works
Fat distribution changes the ratio of waist to neck and hip. The Navy formula converts those ratios into an estimate within about three points of DEXA for most people.
Measure consistently
Same time of day, same tape tension, relaxed. A 2 cm error at the waist moves the result by about 1.5 points.
Is this better than BMI?
For body composition, yes — it separates muscle from fat, which BMI cannot.
How accurate is it?
±3–4% versus DEXA. Good for tracking change, less so for an absolute number.