Design of millimeter wave satellite communication systems must include accurate estimates of the excess attenuation caused by rain. This paper presents a model for estimating the slant path attenuation due to rain. The model is both conceptually and computationally simple, allowing the system designer to easily obtain estimates of link outages caused by rain attenuation. Estimates of attenuation as a function of point rain rate require only the operating frequency, elevation angle, and earth station latitude and altitude. An exponentially shaped spatial rain rate profile is used. The attenuation values as a function of point rainfall rate are coupled with a point rainfall rate distribution to calculate the attenuation distribution (percentage of time that a given attenuation level is exceeded during a year). The rain rate distribution can be obtained from local data sources or can be estimated from global rainfall models. Comparisons of estimated attenuation with measured data from experiments across the world are presented. The level of agreement between model predictions and experimental data is also examined for other models available in the literature.