It has become evident in recent years that carrier concentration profiles measured on beveled surfaces with a spreading resistance probe might not accurately reflect the associated vertical dopant profiles. Carrier spilling, even in the absence of surface states, can move an on‐bevel junction 1/2 micron or more from its metallurgical depth. This article describes a Poisson solver which we have developed for use in spreading resistance data reduction. It allows the calculation of dopant profiles from measured on‐bevel profiles. Examples from a variety of structures are given.