Body Fat Calculator
Estimate your body fat percentage with the US Navy tape method — no calipers needed, just a tape measure and a few body measurements.
The US Navy method (also called the tape or circumference method) estimates body fat from the ratio of a few body measurements to your height. It's the same approach the military uses for fitness assessments — quick, free, and reasonably accurate for tracking changes over time.
How the US Navy body fat formula works
The formula uses the circumference of your neck and waist (plus hips for women), compared against your height. Measurements are taken in inches; if you enter centimetres, the calculator converts them for you.
Women: %BF = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
| Measurement | How to take it |
|---|---|
| Neck | Just below the larynx, tape sloping slightly down at the front |
| Waist | Men: at the navel. Women: at the narrowest point |
| Hip (women) | At the widest point of the hips/buttocks |
| Height | Standing straight, without shoes |
Body fat percentage categories
The American Council on Exercise groups body fat into these ranges. "Healthy" for most people sits in the fitness-to-average bands; essential fat is the minimum needed for normal function.
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25%+ | 32%+ |
Worked example
A man 70 in tall, with a 16 in neck and 34 in waist:
| waist − neck = 34 − 16 | 18 in |
| %BF = 86.010 × log₁₀(18) − 70.041 × log₁₀(70) + 36.76 | 15.5% |
| Category | Fitness |
How accurate is the tape method?
For most people the Navy method lands within a few percentage points of a DEXA scan, and it's excellent for tracking your own progress since it's consistent. It can be less accurate for very muscular or very lean people, where circumference doesn't reflect fat as cleanly. Take measurements at the same time of day and pull the tape snug but not tight for the most reliable trend.