Training estimates

Body Fat Calculator

Enter height, neck, waist, and when needed hip circumference to estimate body-fat percentage with the circumference formula used by this calculator. Treat the result as a tape-measure estimate, not a clinical measurement.

Last reviewed May 18, 2026 by ToolSpilo Editorial Team.

Review method: Reviewed against the implemented formula logic, current CDC or NIH health guidance relevant to the calculator, and its stated limitations.

For educational and tracking purposes only. Results are estimates and are not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional.

Calculator tool

How this calculator works

Use the explanation to understand the formula, assumptions, and practical limits behind the calculator result.

Circumference Formula Used Here

This calculator uses the circumference equations commonly associated with the US Navy tape method and evaluates the measurements after converting centimeters to inches.

For men:

%BF=86.010×log⁡10(waist−neck)−70.041×log⁡10(height)+36.76\%BF = 86.010 \times \log_{10}(\text{waist} - \text{neck}) - 70.041 \times \log_{10}(\text{height}) + 36.76

For women:

%BF=163.205×log⁡10(waist+hip−neck)−97.684×log⁡10(height)−78.387\%BF = 163.205 \times \log_{10}(\text{waist} + \text{hip} - \text{neck}) - 97.684 \times \log_{10}(\text{height}) - 78.387

All dimensions inside the formulas are in inches, even though the user interface accepts centimeters.

Worked Example — Male, 180 cm Height, 85 cm Waist, 38 cm Neck

After conversion:

  • Height: 180÷2.54=70.87180 \div 2.54 = 70.87 in
  • Waist: 85÷2.54=33.4685 \div 2.54 = 33.46 in
  • Neck: 38÷2.54=14.9638 \div 2.54 = 14.96 in
%BF=86.010×log⁡10(33.46−14.96)−70.041×log⁡10(70.87)+36.76\%BF = 86.010 \times \log_{10}(33.46 - 14.96) - 70.041 \times \log_{10}(70.87) + 36.76
%BF≈17.1%\%BF \approx 17.1\%

How to Measure More Consistently

  • Use the same tape and measurement points each time.
  • Keep the tape level and snug, not compressing the skin.
  • Measure under similar conditions, ideally before a meal.
  • Track the trend from repeated measurements instead of over-reading one estimate.

Interpreting the Category

The category bands shown by the calculator are fitness reference ranges, not a diagnosis. Body-fat percentage can help compare body composition over time, but it does not directly measure visceral fat, blood pressure, glucose, lipids, or cardiovascular risk.

Limits to Check

Tape methods are convenient but less precise than laboratory methods such as DEXA. Measurement technique, unusual body proportions, and very high or very low body-fat levels can all shift the estimate. Use the result for tracking, not as a substitute for clinical assessment.

Frequently asked questions

Why must waist be larger than neck for men?

The male formula uses log⁡10(waist−neck)\log_{10}(\text{waist} - \text{neck}). If waist is not larger than neck, the input inside the logarithm is zero or negative and the real-number result is undefined.

How accurate is a tape-method estimate?

It is useful for inexpensive repeated tracking, but it is still an estimate. Small placement differences in waist or neck measurement can move the result by several percentage points, so consistency matters more than chasing one exact reading.

Is body-fat percentage more useful than BMI?

It answers a different question. BMI compares weight with height, while a body-fat estimate tries to describe composition. Neither one alone tells the full health story, especially without waist circumference, lab results, fitness level, and medical context.

Do the calculator categories diagnose obesity or disease?

No. The categories are reference bands for interpretation. They do not diagnose disease, and they do not directly measure visceral fat or cardiometabolic risk.