Petersburg is located at 37°13'40" North, 77°24'6" West (37.227778, -77.401944).
According to the United States Census Bureau, the city has a total area of 23.19 mi2 (60.05 km2). 22.88 mi2 (59.26 km2) of it is land and 0.30 mi2 (0.79 km2) of it is covered by water. The total area is 1.31% water.
Petersburg is located in the Eastern Standard Time (EST) timezone, GMT-05:00. It observes Daylight Saving Time (DST).