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📊 Body Fat Calculator

Calculate body fat percentage using Navy method

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How This Calculator Works

This calculator uses the U.S. Navy circumference method, which estimates body fat percentage based on height and circumference measurements. It's one of the most accessible methods that doesn't require calipers or expensive equipment.

For men: Body Fat % = 86.010 × log10(waist - neck) - 70.041 × log10(height) + 36.76

For women: Body Fat % = 163.205 × log10(waist + hip - neck) - 97.684 × log10(height) - 78.387

The formula was developed by the U.S. Navy to estimate body composition for personnel who don't have access to underwater weighing or DEXA scans. While not as accurate as those methods, it's reliable for tracking changes over time.

Example Calculation

Example: Male, 71 inches tall, 180 lbs, 15.5" neck, 34" waist

Calculation: 86.010 × log10(34 - 15.5) - 70.041 × log10(71) + 36.76 = 86.010 × 1.267 - 70.041 × 1.851 + 36.76 = 109.00 - 129.67 + 36.76 = 16.09% body fat

Category: Fit (14-17% for men is considered fit/athletic)

Fat Mass: 180 lbs × 0.1609 = 29 lbs of fat

Lean Mass: 180 - 29 = 151 lbs of muscle, bone, organs

Interpretation: This person is in the "fit" category with healthy body composition. Ideal body fat for men is 10-17%, and they're within that range.

Common Questions

Is the Navy method accurate?

The Navy method has a 3-4% margin of error compared to DEXA scans (the gold standard). It's most useful for tracking changes over time rather than getting an exact number. If your measurements show you went from 22% to 18% body fat, you've made real progress even if the absolute numbers are slightly off.

What's a healthy body fat percentage?

Healthy ranges vary by sex: Men: Essential fat 2-5%, Athletes 6-13%, Fit 14-17%, Acceptable 18-24%, Obese 25%+. Women: Essential fat 10-13%, Athletes 14-20%, Fit 21-24%, Acceptable 25-31%, Obese 32%+. Women naturally have higher body fat due to biological functions (menstruation, pregnancy, hormones).

How do I measure my waist correctly?

Measure at the narrowest point of your waist (usually at belly button level) without sucking in. Keep the tape level and snug but not compressed into skin. Measure neck at the narrowest point below the Adam's apple. For women, measure hips at the widest point. Take measurements in the morning before eating for consistency.

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