A FORTRAN program is described which uses maximum and minimum temperatures to compute heating and cooling degree days (between and below thresholds, respectively). The temperature cycle is assumed to be a sine wave in which the 1st and 2nd minimum are not necessarily the same. The method is compared With actual planimeter measurements from hygrothermograph charts from Alaska, Arizona, Florida, and Michigan. The data suggest that the bias incurred from the sine wave assumption is somewhat specific to geographical areas. No effect of day length was observed, but in Florida the sine wave method tended to overestimate degree days. A method of correcting for local bias using linear regression is described.