Two unknown values among three electrochemical values, i.e. electrode area, diffusion coefficient, and concentration, are simultaneously obtained by nonlinear regression analysis of a single chronoamperometric faradaic current curve at a microdisk electrode. The approach is an analytical application of the semi-empirical equation presented by Shoup and Szabo for the chronoamperometric response at a disk electrode. To demonstrate the usefulness and accuracy of this approach, the chronoamperometric current at a platinum disk electrode of 50 ${mu}m$ radius in solutions of $Ru(NH_3)_6^{3+},;ferrocene,;Fe(CN)_6^{3-},;and;C_{60}$, were analyzed.