How skinfold measurements work
A skinfold caliper measures the thickness of a double fold of skin and subcutaneous fat at specific anatomical sites. The sum of multiple sites correlates strongly with total body fat when measured consistently by a trained assessor. This calculator supports three established protocols: Jackson-Pollock 3-site, Jackson-Pollock 7-site, and Durnin-Womersley 4-site.
Body density is calculated from the site sum using the protocol-specific equation. Body fat percentage is then derived from density using the Siri formula: %fat = (4.95/density − 4.50) × 100. Different protocols use different site combinations and regression equations validated in different populations.