According to the United States Census Bureau, the town has a total area of 49.0 square miles (126.8 km2), of which 41.7 square miles (108.1 km2) is land and 7.2 square miles (18.8 km2) (14.81%) is water. The Dead Creek and the Hospital Creek run through Addison, and Lake Champlain is on the west border of Addison. The highest point is Snake Mountain, which is 1281 ft above Lake Champlain.