Calculator guide
Body Fat helps you explore the stated health question. Start with the labelled inputs, then review the method, worked example and limitations before using a result.
Formula or method
Convert all inch inputs to centimeters. Male density = 1.0324 − 0.19077 log10(waist−neck) + 0.15456 log10(height). Female density = 1.29579 − 0.35004 log10(waist+hip−neck) + 0.22100 log10(height). Estimated percentage = 495/density − 450. Age and weight are not used.
How to use this calculator
- Enter the sex-specific circumference measurements and height in the displayed units.
- Measure consistently at the specified sites; a circumference estimate is not a direct body-composition measurement.
Worked example
Male height 70 in, neck 15 in, waist 34 in gives approximately 17.4%. Female height 65 in, neck 13 in, waist 30 in, hips 40 in gives approximately 30.8%. Both density equations use centimeters internally.
Understanding the result
Compare the output with the body fat worked example using exactly the same inputs. A different assumption or rounding convention can produce a different displayed result; the output does not establish personal or professional suitability.
Limitations and assumptions
- Historical Hodgdon–Beckett density/Siri estimates, not current Navy eligibility certification. Measurement placement and population differences matter. Reject nonpositive log arguments and percentages outside 0–100; this is not a clinical assessment.
- The worked example demonstrates the stated assumptions, not a recommendation about your personal circumstances.
Frequently asked questions
Which inputs should I check first?
Follow the Body Fat input instructions above. Check each measurement, date, selection or expression before comparing results.
Why might my result differ from another tool?
Compare the other tool's body fat method, input units, rounding and assumptions. A matching title does not guarantee that both tools answer the same question.
Does a linked reference certify this result?
No. A reference can explain a formula or provide background for Body Fat, but it does not endorse this website, validate personal inputs or establish professional suitability.
Sources
Educational and planning information only. Sources are attributed background or formula references, not endorsements. Verify consequential decisions with an appropriate qualified professional.