Portland is located at 41°34'20" North, 72°38'27" West (41.572500, -72.641111).
According to the United States Census Bureau, the town has a total area of 5.46 mi2 (14.15 km2). 4.93 mi2 (12.78 km2) of it is land and 0.53 mi2 (1.37 km2) of it is covered by water. The total area is 9.71% water.
Portland is located in the Eastern Standard Time (EST) timezone, GMT-05:00. It observes Daylight Saving Time (DST).