The earthquake that hit Colombia on July 12, 1785, is one of the seismic events with the highest number of macroseismic studies based on historical sources. Most of these studies have assigned a maximum intensity of VIII to the event. Following the study of Salcedo Hurtado and Castaño Castaño (2011), and applying the Bakun and Wentworth (1997) method and the macroseismic intensity attenuation proposed by Gómez Capera and Salcedo Hurtado (2002), we calculated the magnitude mb = 6.9±0.2 and the macroseismic epicentre at 28 km from Bogotá. The validation of the attenuation model was performed with the instrumental parameters of the earthquake occurred on May 24, 2008, in the same region of the historical earthquake studied in the present article.