Body Fat Formula
The Body Fat Percent formula, specifically the Siri equation, helps estimate your total body fat by using your overall body density, offering a foundational measure for body composition analysis.
Formula
Copy the exact expression or work through it step by step below.
Body Fat Percent = 495 / Body Density - 450 Variables
BFP
Body Fat Percent
The body fat percent value plugged into the body fat calculation.
BD
Body Density
The body density value plugged into the body fat calculation.
Step By Step
- 1
Set the baseline case with the real calculator inputs.
Gender = Male, Weight Kg = 80, Waist Cm = 85, Neck Cm = 38
- 2
Translate rates, periods, and cash values onto the same footing before combining them.
Keep the body fat assumptions consistent instead of mixing monthly and annual views.
- 3
Apply the formula and read the first calculator outputs, not just the headline assumption.
The calculator lands with body fat percent at 16.4%.
- 4
Run one changed scenario so the formula is stress-tested before it is trusted.
The body fat percentage calculator page is the fastest way to compare that second case.
Worked Example
Body Fat sample case
Gender
Male
Weight Kg
80
Waist Cm
85
Neck Cm
38
Body Fat Percent = 495 / Body Density - 450 using gender Male, weight kg 80, waist cm 85, neck cm 38.
The calculator lands with body fat percent at 16.4%.
Common Variations
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Sources & References
- Body Composition Assessment in Adults — National Center for Biotechnology Information (NCBI)
- Estimation of Body Fat from Body Density and Other Measurements — Journal of Applied Physiology
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