The errors associated with using different vertical resolutions for broadband actinic flux calculations have been investigated for the case of a boundary layer cloud. Results are presented for 10, 20, and 40 layers in the lowest kilometer of the atmosphere, with comparisons made against a benchmark of 100 layers. A more accurate picture of actinic flux profiles is obtained by increasing the number of vertical layers. We also derive an expression for the average value of actinic flux within a computational layer. This result, when used to quadratically interpolate the coarser layerings, improved the accuracy in the 10-layer case by a factor of five, when compared with a simple linear interpolation between the original data points.