Pet Mice Size and Weight Chart – How Big do They Grow?

Pet mice go through some rapid changes in the first few weeks after their birth. From little pink babies, they develop into cute furry rodents by the end of the fourth week. Meanwhile, you can see the changes almost on a daily basis as the web on their paws disappear and their ears grow out.

Shortly after, some fur starts to appear and their teeth grow out as well. By the end of the second week, they finally open their eyes and rely on their seeing as well. However, their touching, smelling and hearing are more dominant as their eyesight is pretty weak.

Through all this, you can check exactly in which stage of their development your mice are in in the charts below. In this article, we are not only going to show you these charts but also answer some important questions regarding their age.

Baby Mice Size and Weight Chart

Below, we have included a size and weight chart so that you can see the pace at which mice grow in the first 6 weeks. As you can see, mice rapidly grow in size and weight in the first few weeks. This is why it is preferable to offer them a diet that contains some fats as well.

For example, feeding them wax worms and mealworms is a great way to facilitate their growth. This way, they can also get the protein they need on a daily basis. Once they open their eyes, you can feed them some solid foods as well.

At that point, feeding them cooked vegetables and other vitamins- and mineral-rich foods is also important. In the first two weeks, handling them should be avoided and their mother takes care of the feeding.

Age Size Weight
Week 1 0.5-1 inches 0.5-3 grams
Week 2 1-1.5 inches 3-6 grams
Week 3 1.5-2 inches 7-12 grams
Week 4 2-2.5 inches 13-18 grams
Week 5-6 2.5-3 inches 19-25 grams

Adult Mice Size and Weight Chart

Adult fancy mice also change quite a bit throughout the months. Mice can reach a size of 7-7.5 inches towards their 24th month. Of course, you need to provide them with all the nutrition they need in the meanwhile.

Keeping your mouse on a healthy diet ensures healthy growth and gives them the energy they need throughout the day. It is unusual for mice to live more than 12 months, so chances are that you are not going to see a wild mouse that weighs 42-47 grams.

Pet mice are incredibly lucky because they have a caretaker who can provide them with the healthiest of foods. It is also up to you to minimize the stress your mouse is exposed to in the cage and to ensure healthy sleeping habits.

Age Size Weight (Female-Male avg.)
2 months 3-3.5 23-31 grams
6 months 3.5-4.5 25-34 grams
12 months 4.5-6.5 33-39 grams
24 months 6.5-7.5 42-47 grams

How to Tell the Age of a Pet Mouse?

In the beginning, it is pretty easy to tell the age of a fancy mouse. On the day mice are born, they are completely red and you can even see a milk spot on them. In the next couple of days, their red color turns pink. It is going to be on the second or third day when their ear nubs appear.

After that, it is going to take only another day for the ear flaps to start developing. Before you know it, your mouse has two fully developed ear flaps that are starting to aim a bit backward. The milk spot disappears around day 6, which is also when you can see some fuzz appearing around the neck and ear area.

Two more days and colored fur will start to grow on its whole body, continuing with the belly. It becomes thicker and thicker until the fur is fully grown out on days 10-11. Pet mice also begin to be more active after the fur has fully covered their body.

The next stage around day 12 is when their upper and lower incisor teeth start growing and their eyes start to open. On about day 14, you can start giving them solid food. From then on, their weight is only going to increase.

Beyond that, it is going to be harder and harder to approximate the age of your mouse. It might help to take a look at the charts that we showed above.

Can Pet Mice Live for More than 3 Years?

It is very rare for pet mice to live for 3 years and almost impossible for them to exceed the 3-year mark. Wild mice are only able to live for up to 12 months because of the harsh conditions they live in. With a bit of luck and by keeping your pet on a healthy diet, you might be able to stretch it to 3 years.

This, of course, also depends on the genetics of the mouse. There is a wide range of different types and varieties when it comes to mice and not all of them have the same chances to live for 3 years. You can maximize these changes by taking good care of your mice and minimizing stress factors.

Why Show Mice are Bigger than Regular Fancy Mice?

A show mouse is only a type of fancy mouse that is specifically bred for exhibitions. They can weigh as much as 130 grams while being about 3.1 inches long. Mice are typically brought to shows by competitive breeders that know exactly how to crossbreed, inbreed and line breed mice.

By doing so, they can breed mouse varieties that are bigger or have longer fur than your typical pet mouse. The reason why they are bigger is that the pairs are specifically selected to breed bigger offspring.

These breeders do a great job at line-breeding types of mice that are genetically predisposed to grow big. Not to mention that they feed them a lot because that makes the show mouse look even better.

Wrapping Up

Although there are many types and varieties when it comes to pet mice, it is important to learn more about their stages of growth. We gave you two charts so that you can see how the average pet mouse grows.

The rapid development of mice is very interesting, as they need only 6 weeks to become sexually mature. Moreover, most of their development happens in the first two weeks after their birth, which is amazing. Hopefully, this article has helped you gain a bit of insight when it comes to the development of pet mice.

avatar Jane
Jane is an experienced animal care specialist with a focus on rodents and small mammals, with over 10 years of experience in the pet industry. Her articles provide practical guidance on choosing the right pet and managing common health issues. Jane is an advocate for animal welfare and supports organizations dedicated to protecting wildlife. read more...

Leave a Comment

Your email address will not be published. Required fields are marked *