Calculator
Body Fat Calculator
Estimate body fat percentage using the U.S. Navy circumference method. Enter the measurements required for your selected sex and review the method's limitations.
Estimate body fat percentage
This calculator uses a circumference-based U.S. Navy estimation method. Measurements are entered in inches because the published equation is expressed in inches.
Your estimate
What this body-fat estimate does
This calculator uses a circumference-based U.S. Navy estimation method. It does not measure body fat directly. Instead, it combines height and circumference measurements in a mathematical equation designed to estimate body-fat percentage.
Method and formula
Women: % body fat = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
Measurements are in inches.
The calculator requires the measurements actually used by the equation. Men enter height, neck, and abdominal/waist circumference. Women enter height, neck, waist/abdomen, and hip circumference.
Worked example
A hypothetical set of measurements might be entered as height 70 inches, neck 15 inches, and waist 34 inches for the male equation. The calculator performs the logarithmic equation without asking the user to estimate an unmeasured value. Because the result is an estimate, measurement technique can affect the output.
Measurement quality matters
Use a flexible tape and measure consistently. Small differences in tape placement or tension can change circumference inputs and therefore change the estimate. Repeating measurements under similar conditions can make tracking more consistent, but consistency does not turn the equation into a clinical measurement.
Why different methods disagree
Body-fat percentage can also be estimated with skinfolds, bioelectrical impedance, DEXA, air displacement, and other methods. Each has different assumptions, equipment requirements, and sources of error. A calculator based on circumference should not be presented as clinically exact.
Limitations
- This is an estimation method, not direct measurement.
- Input accuracy strongly affects the result.
- Body shape and formula assumptions can affect accuracy.
- Results from different methods may disagree.
- This tool should not be used to diagnose a condition.
Frequently asked questions
What method does this calculator use?
It uses a circumference-based U.S. Navy body-fat estimation method.
Does it measure body fat directly?
No. It estimates body-fat percentage from height and circumferences.
Why are measurements in inches?
The equation is expressed in inches, so the calculator uses those units directly.
Why does the women's equation require hip circumference?
The selected equation includes height, neck, waist/abdomen, and hip circumference.
How accurate is the estimate?
Accuracy varies with measurement technique, body shape, and the assumptions of the equation.
Can I compare this result with a DEXA result?
You can compare them as different estimates, but they should not be assumed to be identical measurements.
Can a high or low result diagnose a disease?
No. This tool is not diagnostic.
How can I make tracking more consistent?
Measure in a similar way and under similar conditions each time, and focus on trends rather than single readings.