A new functional approximation to the standard normal loss integral

One must consult a table of the standard normal loss integral to determine the reorder point to meet a desired fraction of demand from stock when demand during lead time is stochastic but follows the normal distribution. The table gives the appropriate safety factor. In this article, a simple functional approximation which gives accurate values of the safety factor directly is described, eliminating the need for table lookups and interpolation. The approximation is naturally suited for spreadsheet applications.