The purpose of this text is to present methods for computing drag polars of conventional airplanes at Mach numbers below 1.0. The word conventional is to be interpreted such that airplanes with highly swept, low aspect ratio wings (Л > 35°; A< 4) are excluded.Two methods are presented. First a very fast preliminary design method for estimating drag polars at low Mach numbers. Second a more elaborate (and also more accurate) method for estimating drag polars over the entire range below M = 1.0. The intent is that the first method be used in the very first stages of preliminary design studies of new airplane designs. The second method can be used to obtain more detailed and accurate drag data for an airplane design once its configuration is more or less determined.