📏 Measure neck below larynx, waist at navel level, hips at widest point.

About the Body Fat Calculator

Body fat percentage gives a far more accurate picture of body composition than BMI alone. Two people can have identical BMIs but very different health profiles — one may be a muscular athlete and the other sedentary with high visceral fat. Knowing your body fat percentage helps you track real changes in fat versus muscle over time.

Our Body Fat Calculator uses the U.S. Navy circumference method — a clinically validated technique that estimates body fat from waist, neck, and hip measurements — and cross-checks with BMI-based estimates for comparison.

How It Works

For men: measure neck and waist circumference. For women: measure neck, waist, and hip circumference. The Navy formula converts these measurements into an estimated body fat percentage using a logarithmic equation derived from hydrostatic weighing research.

Formula / Key Reference

Men: Body Fat % = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Women: Body Fat % = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387

Healthy Ranges (American Council on Exercise):

Men: Essential fat 2–5% | Athletes 6–13% | Fitness 14–17% | Acceptable 18–24% | Obese 25%+

Women: Essential fat 10–13% | Athletes 14–20% | Fitness 21–24% | Acceptable 25–31% | Obese 32%+

Real-World Example

Male, 30 years old, 178 cm (70 in) tall

Waist: 85 cm (33.5 in)

Neck: 38 cm (15 in)

Body Fat % = 86.010 × log₁₀(33.5 − 15) − 70.041 × log₁₀(70) + 36.76
= 86.010 × log₁₀(18.5) − 70.041 × log₁₀(70) + 36.76
= 86.010 × 1.267 − 70.041 × 1.845 + 36.76
= 108.95 − 129.23 + 36.76

≈ 16.5%

Result: Fitness category for a male. This indicates a lean physique with good muscle definition. A goal of reaching 13% would move him into the athletic category.

Common Uses

  • Tracking fat loss and muscle gain during a training program
  • Setting realistic fitness goals beyond the scale
  • Evaluating health risk more accurately than BMI alone
  • Military and law enforcement fitness assessments
  • Before-and-after comparisons for fitness challenges

Frequently Asked Questions

How accurate is the Navy circumference method? ▼
Research shows the U.S. Navy method is accurate within ±3–4 percentage points compared to DEXA scanning (considered the gold standard). For most people tracking progress over time, this level of accuracy is more than sufficient — especially since you can use it consistently at home for free.
Where should I measure my waist? ▼
Measure your waist at the navel (belly button) level for men, or at the narrowest point of your torso for women. Stand relaxed, exhale normally, and take the measurement — do not suck in your stomach.
Is body fat percentage better than BMI? ▼
For most fitness and health purposes, yes. Body fat percentage directly measures how much of your weight is fat versus lean mass. BMI only uses height and weight, so it misclassifies highly muscular individuals as overweight and can miss metabolically unhealthy people with low muscle mass.
Can I lower body fat without losing weight? ▼
Yes — this is called body recomposition. By eating enough protein and performing resistance training, you can simultaneously lose fat and gain muscle, keeping your total weight similar while dramatically improving your body composition and health markers.