The quantitative aspects of the breakdown-voltage calculations in reach-through-limited p +− n− n + junctions are revisited, using numerical simulation. It is shown that the conventional abrupt-junction approximation may underestimate the breakdown voltage of diffused epitaxial junctions by as much as 60%, depending on junction depth. Oppositely, but less erroneously, a combined abrupt/linearly-graded approximation overestimates the breakdown voltage by at most 15%. A set of numerically calculated plots are provided for the design of low-voltage power devices.