Body Fat Calculator
Estimate your body fat percentage from a few tape-measure circumferences, using the US Navy method.
Measure at the navel
Estimated body fat
17.5%
Category
Fitness
What Your Result Means
Body fat percentage tells you how much of your body weight is fat versus lean mass (muscle, bone, organs, and water). It's generally a more meaningful measure of fitness than body weight alone, since two people with the same weight can have very different body compositions.
How It Is Calculated
Men: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Women: 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
Worked Example
A man who is 5'10" with a 34" waist and 15" neck has an estimated body fat of about 17.5%, which falls in the "acceptable" range.
Important Assumptions
- Uses the US Navy circumference method (Hodgdon & Beckett, 1984), the most widely used tape-measure body fat formula.
- Measure your waist at the navel and, for women, hips at the widest point, for the most accurate result.
- Accuracy is generally within a few percentage points of more precise methods like DEXA scans.
Frequently Asked Questions
- How accurate is the tape-measure method?
- It's typically accurate within about 3-4% of body fat compared to lab methods like hydrostatic weighing or DEXA scans, which makes it a solid free alternative for tracking trends over time.
- Where exactly should I measure my waist and neck?
- Measure your neck just below the larynx (Adam's apple), and your waist at the navel while relaxed, not flexed. For women, measure hips at the widest point.
Related Calculators
Methodology
This calculator uses the standard US Navy circumference formula. See our methodology page for details.
This calculator provides estimates for educational purposes only. It does not provide medical diagnosis and is not a substitute for professional medical advice. Consult a qualified healthcare provider about your health.