About the Body Fat Calculator
All you need is a simple tape measure. This body fat calculator implements the US Navy circumference method: enter your height, neck and waist measurements in centimetres — women add a hip measurement too — and it estimates your body fat percentage, then places the result in a fitness category running from essential fat through athletic, fitness and average up to high.
Unlike smart scales that guess from electrical signals or skinfold callipers that demand real practice, the tape method feeds simple girth measurements into logarithmic formulas developed and validated by the Naval Health Research Center. It is consistent enough to track monthly progress meaningfully. The whole calculation runs entirely in your browser, so these rather personal numbers never leave your device.
Features
- US Navy circumference method — just a tape measure
- Separate validated formulas for men and women
- Fitness category from essential fat to high
- All measurements entered in centimetres
- Instant estimate, no calipers or scans needed
- Free and completely private in your browser
How to calculate your body fat percentage
- Select male or female — the formulas differ.
- Enter your height in centimetres.
- Measure and enter your neck and waist circumference.
- Women: add the hip measurement at the widest point.
- Read your body fat percentage and category.
Frequently asked questions
How does the US Navy body fat method work?
It estimates body density from the ratio between circumference measurements and height, using logarithmic formulas fitted against underwater weighing data. Men use waist minus neck relative to height; women use waist plus hip minus neck. The result converts to a body fat percentage without any special equipment.
Where exactly do I measure?
Measure the neck just below the larynx, keeping the tape sloping slightly downward at the front. Men measure the waist at navel level; women at the narrowest point, plus hips at their widest. Keep the tape level and snug but not compressing the skin, and measure relaxed, not sucked in.
How accurate is the tape method compared to a DEXA scan?
Studies put the Navy method within roughly 3 to 4 percentage points of laboratory methods like DEXA for most people, with larger errors at the very lean and very heavy extremes. Its real strength is consistency: measured the same way each month, it tracks changes in your body composition reliably.
What is a healthy body fat percentage?
Typical reference bands for men are roughly 6–14% athletic, 14–18% fitness and 18–25% average, with essential fat below 6%. For women the bands sit higher: about 14–21% athletic, 21–25% fitness and 25–32% average. This calculator labels your result using exactly these ranges for your sex.
Should I rely on this number for health decisions?
Treat it as an informative estimate, not a diagnosis. Circumference formulas cannot see how fat is distributed or account for individual build, and no calculator replaces professional assessment. If body composition matters for a medical reason, discuss proper measurement options with a doctor or qualified specialist.