An extinct species of rat that used to live in Southeast Asia is estimated to have weighed around 13 pounds. The largest species of rat alive as of 2014 lives in the Philippines and can weigh up to 4.4 pounds. The largest Norway rat ever caught weighed 2.4 pounds.
A typical common rat weighs less than 0.75 pounds.
Giant Gambian pouched rats have been found in New York City. These rats can be 3 feet long and weigh 4 pounds. The Gambian rats found in New York are probably escaped pets. Imports of giant Gambian pouched rats as pets into the United States were banned in 2003.