Explain it like I'm 12
The body fat calculator converts circumferences to inches and applies the U.S. Navy circumference equations for adult body-fat estimation.
Health & Fitness
Body Fat Percentage Calculator
Estimate body fat percentage from circumference measurements using the U.S. Navy method for adults.
Calculator
Working calculator
Live result18.8% body fatU.S. Navy circumference estimate from height, neck and waist. Measurement consistency matters more than decimal precision.
Formula used
Male: 86.010 log10(waist − neck) − 70.041 log10(height) + 36.76. Female: 163.205 log10(waist + hip − neck) − 97.684 log10(height) − 78.387.
This is the method behind the answer, so the result can be checked rather than simply trusted.Visual grid
This number is one point on a larger pattern
Body Fat Percentage is not just a final answer. It is a step on a line: before and after, input and output, assumption and result.
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InputFormulaResult
18.8% body fatCalculationTime keeps the path visible: the input, the method and the final number belong together.
CalculationTime
Body Fat Percentage Calculation Report
18.8% body fatU.S. Navy circumference estimate from height, neck and waist. Measurement consistency matters more than decimal precision.
Inputs
- Formula sex
- Male formula
- Height
- 178 cm
- Neck circumference
- 40 cm
- Waist circumference
- 90 cm
- Hip circumference
- 100 cm
Method
Male: 86.010 log10(waist − neck) − 70.041 log10(height) + 36.76. Female: 163.205 log10(waist + hip − neck) − 97.684 log10(height) − 78.387.
- For a male-formula adult at 178 cm height, 90 cm waist and 40 cm neck, the equation estimates about 21% body fat.
Assumptions
- Measurements must be consistent and positive.
- Circumference estimates are approximate and can differ from lab methods.
- This is health education only, not diagnosis.
Notes
Use this space on the printed report for client, supplier, classroom, job-location, measurement, quote or approval notes.
Source references
- U.S. Navy Physical Readiness Program — body composition assessment reference
Formula
Male: 86.010 log10(waist − neck) − 70.041 log10(height) + 36.76. Female: 163.205 log10(waist + hip − neck) − 97.684 log10(height) − 78.387.
Worked example
For a male-formula adult at 178 cm height, 90 cm waist and 40 cm neck, the equation estimates about 21% body fat.
Professional note
Master’s Tip: measurement consistency matters more than decimal precision; use the same tape position each time.
Regional and unit assumptions
U.S. Navy circumference method converted from centimetres to inches.
Assumptions and limitations
- Measurements must be consistent and positive.
- Circumference estimates are approximate and can differ from lab methods.
- This is health education only, not diagnosis.
Methodology & Accuracy
How this calculator is checked
CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.
Formula used
Male: 86.010 log10(waist − neck) − 70.041 log10(height) + 36.76. Female: 163.205 log10(waist + hip − neck) − 97.684 log10(height) − 78.387.
Standard or basis
U.S. Navy circumference method converted from centimetres to inches.
Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.Master's Tip
Master’s Tip: measurement consistency matters more than decimal precision; use the same tape position each time.
Related calculators
Questions
Is the Navy method exact?
No. It is a field estimate and can differ from DEXA, hydrostatic weighing or clinical assessment.
Why do measurements matter so much?
Small differences in tape position can change the circumference inputs and therefore the estimate.