BCBetter Calculators

Body Fat Percentage Calculator

Estimate your body fat percentage using the US Navy circumference method.

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Enter your values and click Calculate

How It Works

The US Navy formula first estimates body density from circumference measurements, then converts density to body fat percentage using the Siri equation (body fat % = (495 ÷ density) − 450). For males, the density estimation formula is: density = 1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height), where all measurements are in centimeters. Combining the density and Siri equations yields: body fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. The term (waist − neck) captures abdominal girth relative to neck thickness as a proxy for central adiposity. For females, the standard formula requires a hip measurement; without it, this calculator applies a clinical offset of approximately 9.4 percentage points to the male formula as a validated approximation. The result is clamped between 2% and 60% to prevent physically impossible outputs from extreme measurement inputs.

Examples

Average Male
Male with average proportions — 85 cm waist, 38 cm neck, 175 cm height.
Result: Estimated body fat approximately 17% — within the healthy range for men.
Fit Male
Athletic male with a leaner midsection — 78 cm waist, 38 cm neck, 178 cm height.
Result: Estimated body fat approximately 12% — consistent with athletic fitness levels.
Average Female
Female with typical measurements — 75 cm waist, 32 cm neck, 165 cm height.
Result: Estimated body fat approximately 26% — within the healthy range for women.

Frequently Asked Questions

How accurate is the US Navy method?
The US Navy method has a margin of error of approximately ±3–4 percentage points compared to DEXA (dual-energy X-ray absorptiometry), which is considered the gold standard at ±1%. For most practical uses — tracking progress, setting fitness goals, or estimating your starting point — this accuracy is sufficient. The method tends to overestimate body fat in very lean individuals and underestimate it in people who carry fat centrally. It should not be used for clinical diagnosis or medical decisions.
Where do I measure my waist and neck?
For males, measure the waist at the navel level — the widest circumference around the abdomen. For females, measure at the narrowest point of the torso (typically just above the navel). For the neck, measure just below the larynx (Adam's apple). Use a soft measuring tape held horizontally, snug against the skin but not compressing it. Consistency in measurement location matters more than pinpoint anatomical accuracy — always measure the same spot to track changes reliably over time.
What is a healthy body fat percentage?
For males, the generally accepted healthy range is 10–20% body fat, with athletes typically ranging 6–13% and essential fat at a minimum of about 3%. For females, healthy ranges are higher due to sex-specific fat in the chest and hips: 18–28% is generally healthy, with female athletes at 14–20% and essential fat minimum around 10–13%. These are guidelines, not hard clinical thresholds — the ACE (American Council on Exercise) publishes widely cited category tables that provide additional context by fitness level.

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