Fairfield is located at 40°12'17" North, 74°12'50" West (40.205000, -74.213889).
According to the United States Census Bureau, the township has a total area of 10.45 mi2 (27.07 km2). 10.45 mi2 (27.07 km2) of it is land and 0.00 mi2 (0.00 km2) of it is covered by water. The total area is 0.01% water.
Fairfield is located in the Eastern Standard Time (EST) timezone, GMT-05:00. It observes Daylight Saving Time (DST).