How Many Mice Are Born in a Litter?

If you have a pregnant mouse or problems with mice in your house and want to know how many mice are in a litter – the answer is typically anywhere between 8-12 pups.

There are a lot of variables that affect the litter size. The species, age and health of the mother, and how many previous litters she’s had previously also make a difference.

The largest litter I’ve heard of is 20, so this isn’t out of the question. But I usually expect to see 10 with fancy mice being kept as pets.

How Do Mice Populate So Fast?

House mice are able to increase in numbers really fast. Often turning a few sightings of mice in your home into a serious problem within just a few weeks.

This is because female mice can have several litters a year. Having 40-50 offspring in the span of just 12 months is realistic.

Male mice can reach sexual maturity when they are just five weeks old.  While female mice can start breeding from 12 weeks, and they can be pregnant again within 2-3 months,

The gestation period is only around 20 days too so you can start to get a picture of how quickly mice can breed and rise in numbers.