Fort Duchesne is located at 40°17'16" North, 109°51'14" West (40.287778, -109.853889).
According to the United States Census Bureau, the city has a total area of 7.66 mi2 (19.84 km2). 7.02 mi2 (18.17 km2) of it is land and 0.64 mi2 (1.66 km2) of it is covered by water. The total area is 8.38% water.
Fort Duchesne is located in the Mountain Standard Time (MST) timezone, GMT-07:00. It observes Daylight Saving Time (DST).