When I first got my Teddy I knew he would grow up to be a big hamster – he’s a Syrian male. But I didn’t know exactly how big, and when he’d stop growing.
So I’m helping you figure out how big your hamster can get, based on its breed. And this will help you know how large a cage he will need, and what to expect from your hamster friend.
So when is a hamster fully grown ?
Generally a hamster is fully grown around 3 months of age. This means that the hamster is both sexually mature, and also has reached, or is very close to, its full length.
Of all hamster types, Syrian hamsters grow the largest, and you will notice severe size differences between the baby hamster you brought from the pet shop, and the adult hamster in your cage.
The Dwarf types do grow, but the difference between them as babes and as adults is not nearly as big.
For reference, a baby Syrian around 4 weeks old – when he can be adopted – is about as large as an adult Siberian or Campbell.
But let’s see the differences between each hamster type, since they can grow to different sizes and become mature at slightly different ages.
When is a Syrian hamster fully grown ?
A Syrian hamster is fully grown when he is around 12 weeks of age (3 months). Both males and females are capable of breeding around 4 weeks, so they must be separated to prevent any more litters from producing.
As for size, a Syrian hamster grows to its full size around the 3 month mark. That is when the Syrians become adults, and can reach their full size.
They can reach between 5-8 inches in length, which is 13-20 cm. Some hamsters may grow even larger than that, by a couple of inches/cm, but those cases are rare.
A few traits of adult Syrian hamsters:
- Their markings become clear just before they reach maturity. If they’ve got any darker fur, it will start to show around that time
- The males’ rear ends will become very large, bulging almost. That is where their testicles are, and you will see them often.
- The females will come into regular heat – about every 4 days. You’ll notice them smelling a bit muskier, and they will squeak and hiss if they sense a male hamster.
The average lifespan of a Syrian hamster is 2-3 years, in captivity. They are close to old age when they reach their second birthday, and will start to become slower and have trouble eating and moving around as they reach that age.
When is a Roborovski Dwarf fully grown ?
A Roborovski hamster is a Russian Type, and he will be fully grown around the 3 month mark as well. The Robos can breed as early as 4-5 weeks old, so again they must be separated very early in male and female groups.
Roborovski hamsters reach their full size at around the 3 month mark, reaching up to 2 inches/5 cm. They are the tiniest of the Dwarf types, and are very hard to handle. since they are so hast and agile.
Their fur coloration becomes clear as they reach the 3 month mark. They don’t develop a stripe down their backs, like the Chinese or Campbell for example.
The average lifespan of a Roborovski hamster is about 3-4 years in captivity, but rarely lives past 2 in the wild.
When is a Campbell Dwarf fully grown ?
A Campbell Dwarf is fully grown around the 3 month mark, as the other hamsters. They can breed early, around the time they’re weaned – which is bout 4 weeks old.
Their sizes are about 3-4 inches/ 8-11 cm, and are again hard to handle given their small size and agility. They usually live around 2 years in captivity, but can live a few months past 2 years in the right conditions.
A Campbell’s Dwarf can be recognized by the white belly, and grey-brown fur on their backs, with a much darker stripe going down their backs.
When is a Chinese Dwarf fully grown ?
Chinese hamsters, while not truly Dwarf types, are still much smaller than the Syrian type. A Chinese hamster will become fully grown when he is about 2-3 months old. The hamster can breed before he reaches that point, though.
As for size, the Chinese is larger than most Dwarf types, but smaller than the Syrian. So a fully grown Chinese hamster will be around 3-5 inches/8-13 cm, plus their longer tails. Chinese hamsters have a much longer tail compared to any other hamster types, which can grow to be about an inch long/2-3 cm.
The long tail, and the more slender, long-ish figure of the hamster can make it look a lot like mouse to many people. Given their natural coloring – a sort of brown with a dark stripe down their back – this can be forgiven.
Average lifespan for the Chinese hamster is around 2 years in captivity, but it’s not very well documented in the wild.
When is a Siberian/Winter white fully grown ?
A Siberian, or Winter White, is a type of hamster that does belong to the Dwarf type. They are fully grown at about 3 months of age, and can breed about 4-5 weeks of age.
The Siberian hamster can grow up to 3-4 inches/8-11 cm, and are actually among the easiest to tame hamsters. Their fur can change, depending on temperature and season.
A Winter white is called such because in the wild, its color changes to mostly white. During the summer or warmer season, the color can be a very dark grey, with a stripe going down the hamster’s back.
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When to separate baby hamsters
Separating your hamsters when they’re babies will spare you a lot of troubles, starting with surprise litters and ending with vicious fights between siblings.
So generally, the best time to separate the hamsters into all male and all female groups is when their mother finishes weaning them. This is usually around 4 weeks after the babies are born, and you’ll notice the mother starting to push the babies away if they want to nurse.
You can find much more info now how to properly separate the baby hamsters into gender-specific groups here, as well as how to handle them.
Do take care when the mother has just given birth, since she is easy to startle. A startled, or scared, or stressed out mother can abandon or even eat her babies. Here’s how to make sure your baby hamsters survive, as well as how to make sure the mother is safe and calm during the birth and raising the babies.
The right cage for a fully grown hamster
Your hamster might see so very small when you first get him. That’s the small size they will not keep, as you’ve just found out. Baby hamsters need adult-sized cages.
This is partly because they grow very quickly, and once they do grow they will feel cramped in a cage that is too small for them.
These 5 hamster cages are great picks, depending on what kind of hamster you have.
A cage that is too small for your hamster can lead him to a lot of stress, and feeling irritable most of the time. This can lead to a lot of unwanted behaviors, like chewing the bar cages, and even fighting with their cage mates.
The minimum cage size for an adult Syrian hamster is 24 x 12 inches, and about 12 inches tall. That’s 61 x 30.5 cm, and about 30.5 cm tall.
I’d recommend this to be the size cage you get for your Dwarf type as well, since all hamsters will feel better in a bigger cage, if they have one available. Always get your hamster a bigger cage, even if they look so small they need a large amount of floor space.
Best to read this article on what to know before getting a cage for your hamster, and how to properly care for it. For the Dwarf types I recommend a glass tank, since they can easily escape through the bars of a wire cage. You’ll find info on the glass tank as well in that article.
A word from Teddy
I hope you found what you were looking for here, and can figure out when your hammy is fully grown. For example when I was a baby I was orange all over, with a bit of faded white on my belly.
When I got older I started showing my darker grey markings, and my owners thought I was dirty at first !
So if you want to know more about your hammy, you can read the articles below. You can find out how much water we need, and why we’re sometimes scared of you, and even what food is safe for us.