In late 1992 and early 1993 new standards relating to the determination of flow rates through concentric square-edged orifice meters were published. In some ways, these standards represent a departure from older publications and as such, additional explanation will prove beneficial to some users of the olderstandards. As presented in this document, a description of changes brought on by these new standards is made. Background information is provided to assist those more familiar with the older factored form of the equation. The new and old standards are compared and differences are expounded as they affect implementors of the new equation. Additionally, several example implementation procedures for the new equations are provided, one of which is the implementation chosen by Total flow.