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  • GRR Editorial Team

How Big Can Rats Get: Rat Facts

Most people have likely come across a big rat in their homes or underground places like the New York subway. But how big can rats get? Is there a difference between males and females? Which are the largest rat species in the world?


While public transportation in California is rat-free, there’s a serious issue with big rats in houses. Depending on their species and living conditions, these rats can get large in size and weight.


With that in mind, let’s examine how big rats can get and the different factors that affect their growth. We’ll also take a closer look at how big roof rats and Norway rats get.


a picture of a big rat.

How Big Can Rats Grow


In general, an adult rat will grow to approximately 11 inches. Rats also have very long tails that can reach up to 9 inches. This brings the total length of the average adult rat up to 20 inches. Regarding weight, an adult rat can reach up to 1.1 pounds.


Rats start out very small as babies, with short tails, closed eyes, and ear canals. They won't grow significantly for the first three weeks of their lives, and their body weight will not exceed 0.5 ounces.


Once they’ve weaned completely, they will begin a rapid growth that sees them reach lengths of up to 4 inches and weights of up 4 ounces during the first few months of their lives.


One of the most important factors affecting how big rats get is their environment and food availability. Pet rats live in a safe environment and have access to plenty of food throughout their lives. Comparatively, food can be scarce for wild rats, and their surroundings are full of natural predators.


Therefore, a pet adult rat can reach an even larger size compared to a wild adult rat. Still, wild and domesticated rats have approximately the same size during their infant stages.


Male vs. Female Rats Size


Another important factor regarding how big rats can get is their gender. There are countless examples in nature where one gender can have a significantly larger size than the other.


The same is applied to rats, where adult males are usually bigger than adult females. Specifically, the maximum weight a wild adult male rat can reach is 1.1 pounds, whereas females can barely reach up to 10 ounces.


However, access to an abundance of food can cause rats to grow significantly more. For instance, a pet female rat can reach up to 1.1 pounds, the same as a wild male rat. Similarly, a pet male rat can reach a whopping 1.76 pounds.


How Big Are Rats


Even the most common rats can grow to very large sizes. But the question remains; How big can rats get? What’s the largest rat species in the world?


There are many large rat species around the world. One of the biggest ones is the Sumatran bamboo rat. Its usual body size reaches up to 20 inches, and it has a relatively short tail, at around 8 inches long.


As the name suggests, this rat can be found in Sumatra and parts of China and feeds on bamboo and sugarcane. This rich diet leads to an enormous weight of up to 8.8 pounds, making it the heaviest rat species in the world.


What Is the Largest Rat in the World?


The largest, most commonly found rat, in terms of total length, is the Gambian pouched rat which is very common in sub-Saharan Africa. It was imported in Grassy Key, Florida, for pet breeding, but a few of them managed to escape and establish a population in the early 2000s.


The size of the Gambian pouched rat can reach up to 35 inches in total length thanks to its extremely long tail (up to 18 inches). Their average weight is approximately 3 pounds.

The biggest Gambian pouched rat was a whopping 3 feet long and weighed around 3 pounds.


Comparatively, the largest Sumatra bamboo rat was only 1.6 feet in length but had a massive weight of 8.8 pounds.


How Big Do Roof Rats Get


Roof rats can reach considerable sizes. Their body length is usually around 6 to 8 inches, but their long tail makes their total length reach up to 16-17 inches. While their average body weight is about 5 to 9 ounces, they can sometimes weigh up to 12 ounces.


How Big Do Norway Rats Get


Norway rats, also known as brown rats, are more common than roof rats and bigger in size. Their typical body length is around 10 inches, and their long tail makes them even lengthier at up to 20 inches.


Brown rats are also significantly heavier than black rats. While females only weigh up to 12 ounces, a male’s total weight can reach up to 20 ounces. Some huge ones can even weigh up to 2 pounds.


Let Our Big Team Take Care of the Big Rats


If you’ve suffered from rat problems before, you know how big rats can get. Even if you have experience dealing with them, a rodent control expert is sometimes necessary.


At Green Rodent Restoration, we utilize our knowledge, years of experience, and the best repair and rodent removal tools to ensure you won’t get any rodent issues ever again!


Call us now if you’re struggling with a rat infestation. We’ll give you a free quote and ensure the removal of any pests for good!


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