The slope mass rating (SMR) method is universally used for the characterization and classification of rock slopes. SMR is calculated by reducing the value of basic rock mass rating (RMRb) by subtracting three adjustment factors F1, F2, and F3 based on the geometrical relationship between the slope and discontinuity and adding one adjustment factor F4 depending upon the excavation method used. These adjustment factors (F1, F2, and F3) are mathematical functions (continuous/discrete) that require post-processing of field data on a computer for their derivation. Less work has been done to develop the charts for the direct calculation of SMR in the field. In this paper, SMR charts are developed for the onsite classification of rock slopes. With the aid of SMR charts, an engineering geologist can easily assess the onsite SMR class of rock slopes by plotting discontinuity dip amount (plunge amount in case of wedge failure) and strike parallelism between slope dip direction and discontinuity dip direction (slope dip direction and trend direction of intersection line in case of wedge failure). Using SMR charts for any project (open-pit mines, road cut slopes, natural slopes, etc.) onsite suggestions of proper remedial and preventive measures for the rock slopes can be given, which accelerates the overall preliminary slope mass classification process. The proposed SMR charts are straightforward to use and can be adopted as useful tools for the preliminary rock slope stability assessment.