Westerly is located at 41°22'37" North, 71°49'39" West (41.377222, -71.827500).
According to the United States Census Bureau, the town has a total area of 16.49 mi2 (42.71 km2). 15.97 mi2 (41.37 km2) of it is land and 0.52 mi2 (1.34 km2) of it is covered by water. The total area is 3.14% water.
Westerly is located in the Eastern Standard Time (EST) timezone, GMT-05:00. It observes Daylight Saving Time (DST).