Skinfold Body Fat (3-Site) Calculator

About this calculator

The Jackson-Pollock 3-site skinfold equation estimates body density from three caliper measurements — chest, abdomen and thigh for men; triceps, suprailiac and thigh for women — combined with age in a regression formula, since body fat distribution and skin compressibility both shift with age. That body density is then converted into a body fat percentage using the Siri formula (%BF = (495/density) − 450), which models the body as a two-compartment system of fat mass and fat-free mass with different known densities.

This calculator takes your sex, age and the appropriate three skinfold measurements and returns your estimated body fat percentage using the Jackson-Pollock and Siri equations together. Personal trainers and strength coaches tracking client body composition over time, exercise science students learning field-based body composition methods, and athletes monitoring fat mass changes during a training cycle use it as a low-cost, portable alternative to DEXA or hydrostatic weighing, with the caveat that accuracy depends heavily on consistent, well-trained caliper technique.