How Big Do Rats Get?

When considering how big do rats get, it’s important to realize that their size is not limited to the size of the cage. The typical size of a rat is about the same as that of a dog or a cat. The biggest differences in size between a female rat and a male rat are in their reproductive capabilities. Rats are able to reproduce when they reach five weeks of age and the gestation period lasts for about 21 to 23 days. Female rats can conceive up to five times a year and have litters of seven to fourteen young.

Rats weigh between one and three pounds, although some exotic breeds are much bigger. The Gambian pouched rat, for example, can grow to nine pounds in size. This breed is brought in by the black market, like puppies, and can be quite dangerous if it gets too big. Despite this, the average city rat weighs only one to two pounds.

The smallest rat species is the Osgood’s Vietnamese rat, which is five to seven inches long. In contrast, the biggest rat species in the world is the Sumatran bamboo rat, which can grow up to twenty inches long. While common rats are not very large, overfeeding can lead to overweight rats.