Body Fat Percentage Calculator
Estimate your body fat percentage using the US Navy tape-measure method. Enter your height, waist, neck, and (for women) hip measurements to get an instant result without specialist equipment.
About this calculator
The US Navy body fat method uses circumference measurements and logarithmic equations to estimate body density and derive fat percentage. For men, the formula is: BF% = 495 / (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. For women, hip circumference is added because women carry more fat in the hip region: BF% = 495 / (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450. All measurements are in centimetres. The constants 495 and 450 are derived from the Siri equation, which converts body density to fat percentage. This method is widely used by the US military for fitness assessments and correlates well with DEXA scan results for most body types.
How to use
Example: a female with height = 168 cm, waist = 78 cm, hip = 98 cm, neck = 33 cm. Step 1: waist + hip − neck = 78 + 98 − 33 = 143. Step 2: log₁₀(143) ≈ 2.1553; log₁₀(168) ≈ 2.2253. Step 3: denominator = 1.29579 − 0.35004 × 2.1553 + 0.22100 × 2.2253 ≈ 1.29579 − 0.75446 + 0.49179 = 1.03312. Step 4: 495 / 1.03312 ≈ 479.2. Step 5: 479.2 − 450 = 29.2%. This woman's estimated body fat is approximately 29.2%.
Frequently asked questions
How accurate is the US Navy method for calculating body fat percentage?
The US Navy method typically falls within 3–4 percentage points of DEXA scan results for most average-build adults. Accuracy can decrease for very muscular individuals, since a large neck circumference inflates the waist-minus-neck ratio and can underestimate fat. It is far more accessible than hydrostatic weighing or DEXA, requiring only a flexible tape measure. For tracking trends over time rather than pinpointing an exact number, it performs reliably when measurements are taken consistently under the same conditions.
What is a healthy body fat percentage for men and women?
For men, essential fat sits around 2–5%, athletes typically range from 6–13%, a fitness level spans 14–17%, and acceptable health ranges extend to 24%. For women, essential fat is 10–13%, athletes 14–20%, fitness 21–24%, and acceptable up to 31%. Values above these ranges are generally classified as obese. These thresholds reflect widely cited American Council on Exercise (ACE) guidelines, though small variations exist between health organisations.
Why does the women's body fat formula include hip circumference but the men's formula does not?
Women naturally store a greater proportion of body fat around the hips and thighs — a pattern known as gynoid or pear-shaped fat distribution — making hip circumference a meaningful predictor of total fat mass in females. Men primarily store excess fat around the abdomen (android or apple-shaped distribution), so waist and neck measurements alone capture most of the predictive variation. Including hip circumference in the male equation would not improve accuracy and could introduce noise into the estimate. The US Navy validated separate sex-specific equations based on these physiological differences.