This aid consists of three specially designed charts for determining the number of teaching stations required to house any given enrollment of pupils in any subject. Further uses are to determine class size, to discover the adequacy of proposed multi-purpose rooms, and to compute the fraction of a school day any room will be used. A specific example is used to familiarize the reader with the five steps used in the formula. An educational program is also presented to show how the formula is used in a realistic situation. (RH)