Body fat % estimator

About this calculation

The U.S. Navy circumference method (Hodgdon & Beckett, 1984) estimates body fat percentage from tape-measure circumferences plus standing height. It was developed for Navy body composition screening as a low-cost alternative to hydrostatic weighing, and remains widely used in fitness and military contexts.

The formula (metric)

Men: BF% = 495 / (1.0324 − 0.19077 · log₁₀(waist − neck) + 0.15456 · log₁₀(height)) − 450.
Women: BF% = 495 / (1.29579 − 0.35004 · log₁₀(waist + hip − neck) + 0.22100 · log₁₀(height)) − 450. Imperial inputs are converted to centimetres before evaluation.

How to measure

Use a flexible, non-stretching tape and keep it level, snug, but not compressing the skin. Measure while standing relaxed and breathing normally.

• Neck — just below the larynx (Adam's apple), tape perpendicular to the long axis of the neck.
• Waist, men — at the level of the navel, horizontally around the body. Note: this is different from the “narrowest point” landmark used by BMI and waist-to-height ratio; the Navy formula was calibrated against the navel measurement and needs that specific spot for accurate body-fat estimates.
• Waist, women — at the narrowest point, typically just above the navel (same landmark as BMI and waist-to-height ratio).
• Hip, women — at the widest point of the buttocks, tape horizontal.

See the full how to measure your waist correctly guide for the common mistakes that shift the reading.

Category context

The category labels (Essential fat, Athletes, Fitness, Acceptable, Obese) are the widely cited American Council on Exercise (ACE) body fat ranges. They differ by sex because women carry more essential fat than men (reproductive and hormonal function). Athlete ranges overlap with the lower end of the healthy range for highly trained individuals.

Accuracy and limitations

The Navy method typically estimates body fat within roughly 3–4 percentage points of hydrostatic weighing or DEXA across the general population. Accuracy decreases at the extremes of body composition (very lean, very obese, or heavily muscled individuals), and depends heavily on consistent tape placement. It is a screening estimate, not a clinical measurement.

Medical disclaimer. This calculator is for general educational use and is not medical advice, diagnosis, or treatment. Body composition estimates do not replace clinical assessment. If you have concerns about your weight, body composition, or health, consult a qualified healthcare professional.