Abstract: Nomograms are generated to determine the top and bottom boundaries of a geological structure using the residual gravity anomalies of a vertical cylinder. The nomograms are estimated using the corresponding axis values (x_3/4 and x_1/4) of the ¾ g_max and ¼ g_max , which are determined from the residual gravity anomaly. In addition, a small computer code based on equations representing the nomograms provides simple and fast interpretation. The amplitude coefficient can be easily determined due to the top and bottom depths of the vertical cylinder are known from the interpretation of the residual gravity anomaly. The validity of the method is approved with synthetic data sets and then applied to observed data set.