Several different formulas, providing divergent results, exist for calculating free testosterone concentration. This calculator utilises the Anderson's formula S-Testo-Free (pmol/l) = S-Testo (nmol/l) x (2.28-1.38 x log (SHBG (nmol/l)/10)) x 10.
Various laboratories have different reference values. It is recommended to request the laboratory one uses to provide the result directly as calculated free testosterone and to compare the result with the reference values of the respective laboratory.