First, one needs to distinguish between a rat and a mouse. A mouse is generally smaller than a rat, but a young rat can wrongly be identified as a mouse.

Differences between mice and rats

• While will prefer to feed on cereal grains and plants, rats prefer to eat fresh grain and wheat. However, both animals will eat nearly anything they find.
• Using any soft material available, a mouse will build its nest somewhere hidden but close to a source of food while a rat will create a burrow just about anywhere for shelter.
• Though a female mouse breeds more times a year, the number of young ones per litter is less as compared to that of the few times but a large number per litter. For instance, a mouse can produce up to 10 litters a year with 5 to 6 per litter while a rat can breed 6 litters of up to 12 young ones per litter annually.
• Mice reach sexual maturity at the age of 6months while rats can start reproducing while as young as 3 months old.
• The lifespan of a mouse is 1 year while rats can live up to 1 year and a half.
• While you can distinguish a mouse by its fur and body structure, the fur of a rat is much coarser and dull in colour with larger heads and feet, unlike the mouse.

What if it is you can’t tell if it is a small rat or a mouse?

• The head of a mouse is small, usually directly proportional to its body while a young rat’s head is large for its body size.
• A mouse has a more pointed muzzle unlike a small rat which has a rather blunt muzzle.
• The tail length of a mouse is usually same size as the body length while a small rat has a shorter tail than the length of its body.
• The ears of a mouse are largely unproportional to their head size while those of a young mouse are tiny, just perfect for their head size.
• Small and proportional to their body is a mouse’s feet unlike those of a young rat which are large to their body.

How big can a mouse grow?
An average mouse will weigh between 23g and 28g and have a body length ranging from 2cm to 18cm.



Weighing less than 1g with a body length of between 3cm and 7cm is the African pygmy. It is the smallest mouse on earth.

However, the largest mouse ever in the world was named Gary. This mouse is as big as the size of a dog. It is a pet owned by a couple living in South America.

Read the How to get rid of mouses page for helpful information and to learn more about How big do mice get?

How big do mice get?