A formula is presented for computing the field in axial-field permanent-magnet motors, The formula is based on ii three-dimensional (3-D) analytical analysis and is expressed in terms of a finite sum of elementary functions, It is readily programmed and ideal for parametric studies of field strength. It is also well suited for parallel processing and could be developed into a motor model for real-time performance simulations, It is applied here to a practical motor geometry and verified by the use of 3-D finite element analysis (FEA).