In an attempt to find the most suitable method for determining the equivalent square for two commonly employed blocked field arrangements, a comparison of measured outputs was made for four different treatment machines. The machines varied by manufacturer, design, and energy. The fields in question were a midline-blocked field and a half-blocked field. The data obtained was used to streamline calculations made by technologists for the original treatment setting. It was further used to enhance the accuracy of computer-generated verification of the original setting. The authors recommend that each institution employing such fields consider obtaining similar data for their own treatment machines.