Body Fat Percentage Calculator
Estimates body fat percentage from waist, neck, and hip circumferences using the U.S. Navy tape-measure method. Use it to track changes in body composition without calipers or expensive lab scans.
About this calculator
The U.S. Navy circumference method estimates body density from simple tape measurements and then converts that to a body fat percentage. For men, the formula is: % body fat = 495 / (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. For women, the hip measurement is added because fat distribution differs: % body fat = 495 / (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450. All measurements are in centimeters and height is in centimeters. The method has an error margin of roughly ±3–4 percentage points compared to DEXA scanning, but its consistency makes it excellent for tracking trends over time rather than as an absolute value.
How to use
Example for a male with waist = 85 cm, neck = 38 cm, height = 175 cm: waist − neck = 47 cm. log₁₀(47) ≈ 1.6721; log₁₀(175) ≈ 2.2430. Denominator = 1.0324 − (0.19077 × 1.6721) + (0.15456 × 2.2430) = 1.0324 − 0.3191 + 0.3466 = 1.0599. % body fat = (495 / 1.0599) − 450 ≈ 466.9 − 450 ≈ 16.9%. That falls in the 'Fitness' category for adult men (14–17%). Measure consistently each time — same time of day, same tape tension — to make comparisons meaningful.
Frequently asked questions
How accurate is the U.S. Navy body fat formula compared to DEXA or hydrostatic weighing?
The Navy tape method typically falls within ±3–4% of DEXA or hydrostatic weighing results for most people, which is acceptable for general fitness tracking. It tends to underestimate body fat in very obese individuals and can be less precise for athletes with unusual fat distribution. DEXA remains the gold standard because it distinguishes bone, lean mass, and fat directly. For home use, the tape method's low cost and consistency make it a practical alternative when used at regular intervals.
What body fat percentage is considered healthy for men and women?
For men, essential fat is 2–5%, athletes range from 6–13%, fitness enthusiasts 14–17%, acceptable health 18–24%, and obesity starts above 25%. For women, essential fat is 10–13%, athletes 14–20%, fitness 21–24%, acceptable 25–31%, and obesity above 32%. These ranges are defined by the American Council on Exercise. Age also matters — body fat naturally increases with age even when weight stays stable, so age-adjusted norms are more meaningful for older adults.
How should I measure my waist and neck correctly for the body fat calculator?
Measure your waist at the narrowest point, typically just above the navel, while relaxed and not sucking in. For the neck, measure just below the larynx (Adam's apple) on a slight downward slope. Women should also measure the hips at the widest point across the buttocks. Use a flexible tape measure pulled snug but not compressing the skin, and take each measurement twice to confirm consistency. Measuring at the same time of day — ideally in the morning before eating — reduces day-to-day variability.