Body Fat Percentage Calculator
Estimate body fat percentage using measurements.
Estimating body fat with a tape measure
Body fat percentage tells you what share of your weight is fat rather than muscle, bone and water — the thing BMI cannot see. This calculator uses the US Navy circumference method, which needs only a tape measure and gets within about three to four percentage points of a clinical scan. It is the most practical way to track composition at home over months.
How to use the Body Fat Percentage Calculator
- Choose your Sex — women include a hip measurement, men do not.
- Enter your Height (cm).
- Measure your Neck just below the larynx and your Waist at the navel.
- Women also enter Hip at the widest point. Keep the tape snug, not tight.
Formula and a worked example
Men: 495 ÷ (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450
Women: 495 ÷ (1.29579 − 0.35004·log10(waist + hip − neck) + 0.22100·log10(height)) − 450
All measurements are in centimetres. The method works because fat distributes predictably around the waist and hips relative to the neck, which stays comparatively lean.
Worked example
A man 180 cm tall with a 38 cm neck and 90 cm waist comes out at roughly 20% body fat — average for his age group. Losing 6 cm from the waist with the neck unchanged would drop that to about 15%.
Typical ranges
- Men — essential 2–5%, athletes 6–13%, fitness 14–17%, average 18–24%, high 25%+
- Women — essential 10–13%, athletes 14–20%, fitness 21–24%, average 25–31%, high 32%+
Frequently asked questions
How accurate is the Navy method?
Usually within three to four percentage points of a DEXA scan. Its real strength is consistency — measured the same way each time, it tracks change reliably even if the absolute number is slightly off.
Where exactly do I measure my waist?
At the navel for men; at the narrowest point for women. Stand relaxed, breathe out normally, and do not pull the tape tight.
Why does the women's formula need a hip measurement?
Women carry proportionally more fat around the hips and thighs, so waist alone would understate it.
Is body fat percentage better than BMI?
For assessing composition, yes — it separates muscle from fat. BMI is faster and needs no tape, which is why clinics still use it as a first screen.
Related calculators
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