This article is written not to teach the reader HOW to size control valves, but how to look at a valve data sheet and know if the factors fall within the proper range, and thus if the information can be trusted. The factors that go into valve sizing are covered, and a general description is given on how those factors are derived. Most importantly, the ranges delivered in the tables can be used as a quick reference for the end user or plant engineer to decipher if the values given were calculated correctly. This article is written by myself, John Roper on behalf of Yeary Controls. Please enjoy and contact me at jroper@yearycontrols.com if you have any questions or comments.