Health
Body Fat Calculator
Estimate your body fat percentage with nothing but a tape measure. The US Navy circumference method uses your height, neck, and waist (plus hips for women) — and lands within about ±3% of far more expensive methods for most people.
Estimated body fat
16.9%
Category
Fit
Uses the US Navy circumference method — accurate to roughly ±3% for most people. Measure with a flexible tape: neck below the larynx, waist at the navel (relaxed, not sucked in), hips at the widest point. Not medical advice.
How it works
The Navy method exploits a simple observation: fat accumulates predictably at the waist (and hips), while the neck stays comparatively lean. The gap between those circumferences, scaled by height, tracks total body fat remarkably well.
Measure accurately or the estimate drifts: neck just below the larynx, waist at the navel while relaxed (don't suck in), hips at the widest point. Take each measurement two or three times and average, ideally in the morning before eating.
Body fat percentage tells you more than BMI because it separates fat from muscle. A muscular 90 kg lifter and a sedentary 90 kg office worker can share a BMI while their body fat differs by 20 points — this method sees the difference; BMI can't.
Men: BF% = 495 / (1.0324 − 0.19077·log₁₀(waist − neck)
+ 0.15456·log₁₀(height)) − 450
Women: BF% = 495 / (1.29579 − 0.35004·log₁₀(waist + hip − neck)
+ 0.221·log₁₀(height)) − 450
(measurements in cm)Frequently asked questions
What is a healthy body fat percentage?
Typical fitness guidelines: for men, 6–13% is athletic, 14–17% fit, 18–24% average, 25%+ obese. For women (who carry more essential fat): 14–20% athletic, 21–24% fit, 25–31% average, 32%+ obese. Essential fat minimums are ~3% for men and ~12% for women.
How accurate is the Navy tape method?
Studies put it within about ±3% of DEXA scans for most people — comparable to consumer bioimpedance scales and far better than BMI alone. It's least accurate at the extremes: very lean athletes and very high body fat levels.
When and how should I measure for consistent results?
Same conditions every time: morning, before food, tape snug but not compressing the skin, standing relaxed. Track the trend across weeks rather than reacting to any single reading — day-to-day water shifts move the numbers.
Why do women need the hip measurement?
Fat distribution differs by sex: women store proportionally more fat at the hips and thighs, and less at the waist, so a waist-only formula would underestimate. Adding the hip circumference restores accuracy.
Is body fat percentage better than BMI?
They answer different questions. BMI is a fast population-level screen; body fat percentage actually distinguishes muscle from fat, which matters if you train. Best practice is tracking both plus waist circumference — and remember neither is medical advice.