Navy circumference body-fat equation and measurement limits
Estimate body fat percentage from height, neck, waist and—when required by the equation—hip circumference.
This page provides an equation-based estimate for education and planning. It does not diagnose a condition, measure an individual response, or replace professional care.
How to use this health calculator
- Choose appropriate inputs: Enter measurements using the units and ranges shown.
- Review the assumptions: Confirm that the model applies before interpreting the result.
- Calculate and interpret: Read the result together with its limitations and cautions.
- Use professional guidance when needed: Do not use a general calculator to change medication, treatment, or a clinician-directed plan.
Formula and variables
All circumferences are converted to centimeters before the equation. The binary sex selection chooses the published sex-specific model and does not determine gender identity.
Male density = 1.0324 − 0.19077 log10(waist − neck) + 0.15456 log10(height); female density = 1.29579 − 0.35004 log10(waist + hip − neck) + 0.221 log10(height); body fat % = 495 ÷ density − 450- height — Height
- Standing height without shoes.
- waist — Waist circumference
- Horizontal circumference at the site specified by this method.
- neck — Neck circumference
- Tape measurement below the larynx.
- hip — Hip circumference
- Widest horizontal circumference, used by the female equation.
Worked example: male equation in metric units
A user selects male and enters height 175 cm, neck 37 cm and waist 85 cm.
- Height
- 175 cm
- Neck
- 37 cm
- Waist
- 85 cm
- Circumference value = 85 − 37 = 48 cm.
- Apply log10(48) and log10(175) to the density equation, then convert density to percent fat.
Result: The equation returns a circumference-based body-fat estimate.
This is a prediction from external measurements, not a direct measurement of fat mass or distribution.
Understanding your results
Equation result
The numerical output follows the displayed formula and entered assumptions.
Personal interpretation
Individual biology, measurement error, environment, health conditions and medicines can change real-world outcomes.
Assumptions
- The measurement sites and tape tension are consistent with the displayed protocol.
- Height and circumferences use the selected unit system.
- The selected equation input matches the published model the user intends to apply.
Limitations
- Individual error can be several percentage points even when measurements are consistent.
- Neck muscularity, abdominal shape, loose skin and body-fat distribution can bias the estimate.
- Different methods such as DXA, skinfolds and bioimpedance are not directly interchangeable.
- The binary sex-specific equations do not represent every body or clinical circumstance.
Common mistakes
- Measuring the waist at a different anatomical site between checks.
- Compressing the skin with the tape.
- Comparing a Navy estimate directly with a different method.
- Interpreting a small change as real when it may be measurement noise.
Practical use cases
Educational estimate
Explore how the inputs affect the equation result.
Consistent tracking
Compare estimates only when methods, units and conditions are consistent.
Planning and decision guide
Treat cautions as part of the result
Body-fat percentage alone does not diagnose health, fitness, nutritional status or an eating disorder.
Avoid repeated checking if body measurements cause distress or support restrictive or compulsive behavior; seek appropriate professional support.
Escalate symptoms or clinical questions
Seek qualified medical advice for symptoms, diagnosed conditions, medicines, pregnancy, or individualized treatment decisions.
Frequently asked questions
How accurate is the Navy method?
It is a field prediction with meaningful individual error; consistent technique improves tracking but does not make it a direct measurement.
Why is hip circumference requested only for one equation?
The published female equation includes hip circumference, while the male equation uses waist minus neck.
Can I compare this result with a smart scale?
Not as though they are identical. The methods use different models and may have different biases.
Sources and review
- Circumference-Based Predictions of Body Fat Revisited: Preliminary Results from a US Marine Corps Body Composition Survey — Frontiers in Physiology via PubMed Central. Accessed 2026-08-03.
- Validity of Percent Body Fat Predicted from Circumferences: Classification of Men for Weight Control Regulations — Military Medicine (PubMed record). Accessed 2026-08-03.
- Development and Cross-Validation of a Circumference-Based Predictive Equation to Estimate Body Fat in an Active Population — Obesity Science & Practice (PubMed record). Accessed 2026-08-03.
Reviewed 2026-08-03.