Abstract The square-wave potential-time sequence treated here is composed of a square wave with a large amplitude superimposed on a staircase with a small step height. Current measurements are made at the end of the pulse in each square-wave half cycle and the difference of these two currents is plotted against the staircase potential. An equation describing the resulting voltammetric curve is derived for a reversible electrochemical system assuming arbitrary electrode geometry, and is expressed as a simple product of a geometrical term and a potential term. Therefore the normalized voltammetric response, which is a bell-shaped curve with a peak at a formal potential, does not depend on shape or size of electrodes. This finding is verified with numerical calculation for various electrode geometries. Approximate equations for the peak current and the peak width at half height are presented.