Lorton is located at 38°42'14" North, 77°13'41" West (38.703889, -77.228056).
According to the United States Census Bureau, the city has a total area of 12.47 mi2 (32.29 km2). 12.38 mi2 (32.07 km2) of it is land and 0.09 mi2 (0.22 km2) of it is covered by water. The total area is 0.69% water.
Lorton is located in the Eastern Standard Time (EST) timezone, GMT-05:00. It observes Daylight Saving Time (DST).