How Big Does a Guinea Pig Get?
When is a Guinea Pig Fully Grown?
A guinea pig is considered fully grown around 3 months of age, or 16 weeks. Guinea pigs are an animal that grows incredibly quickly and will complete most of their growing around 8 weeks. After 8 weeks, they continue to grow but at a much slower rate until they reach 16 weeks. While your full grown guinea pig may approach adulthood in the blink of an eye, you will never forget the baby stage!
Guinea pigs are a precocial animal, meaning they are born fully formed, with their full eyesight, hearing and can move around independently from the mother. Precocial young often don’t have any development left to do outside of the womb, and just need to focus on growing to full size.
From about 6 months to 5 years is when a guinea pig is considered an adult, and anything older would be a senior piggy.
Female Guinea Pig Size
The female guinea pig size is typically a litter smaller than males. Female guinea pigs tend to weigh 2 – 2.5 pounds, which is about 700 – 1100g. They also grow a little shorter in length on average, between 8 – 12 inches, which is 20 – 30cm.
The breed of guinea pig can influence the specifics on their size, so it’s not uncommon to see a guinea pig not fit into these ranges.
Male Guinea Pig Size
The male guinea pig is the bigger sex of the species on average, with males weighing between 2.2 – 3.5 pounds, which equals to 1000 – 1500g. They do grow to be longer in length than females, averaging 10 – 16 inches or 25 – 40cm.
Just like with females, the male guinea pig size can vary away from the average depending on the specific breed, or their overall genetics.
A pair of guinea pigs hanging out
What is the Biggest Domestic Guinea Pig Breed?
Just like with any animal, the different breeds within the species can come with great variety in their physical appearance. For the most part, the changes from breed to breed in guinea pigs are mainly differences in their fur colours, patterns and length. However, there are some breeds that get a little bigger than others.
The Rex guinea pig is undoubtedly the largest domestic breed of guinea pig. These often reach about 17 inches as a full grown guinea pig and are most likely to hit the higher weight average.
If you’re interested in learning more about the Rex breed, or any other breed, then we have a great list highlighting the best features of each one right here.
World-Record Breaking Guinea Pig
While thinking about the current guinea pig size, I’m sure you’re curious as to what the biggest guinea pig in the world ever was. Well, it was certainly extremely different from our domestic breeds today.
The largest guinea pig discovered was believed to be over 1500 pounds and 9 feet long. For context, this is roughly the size of a large buffalo! This guinea pig was discovered by a team of Venezuelan researchers who dug up the fossil in a South American desert. This guinea pig was later named Goya and is undoubtedly the most impressive of the record breaking guinea pigs. Goya was predicted to have lived over 8 million years ago and roamed the South American banks of Urumaco.
Comparing Goya to the domestic guinea pig surely makes the brain hurt a little bit, it’s incredible thinking about how nature evolves! Just imagine if guinea pigs remained that size, they would certainly be a little awkward to keep as a house pet.
How Much Space Does a Guinea Pig Need?
When planning to bring guinea pigs into your home, it’s also good to consider their guinea pig size in comparison to the space available that you wish to provide them. It’s important to remember guinea pigs are highly social animals and require at least one friend to keep them happy.
When planning their enclosure space, always consider the minimum for 2 piggies.
Enclosure Sizes
Both the RSPCA and American Humane Society agree and state the minimum enclosure space for a guinea pig is 7.5 square feet. This space can be great for a single guinea pig that has frequent access outside of their enclosure and can freely run around to get extra exercise.
The cage minimum remains the same when including a second guinea pig and increases by 2.5 – 3 square feet per guinea pig being housed. This may seem like a lot of space when picturing it, or seeing it planned out in your room, but in reality, it’s not much at all. These suggestions are the absolute minimum a guinea pig should be kept in, and once you add in the hutches, toys, tunnels and extra items, the space is greatly reduced.
To get a better estimate on the sizes, the recommendation is to add about 3 square feet to every minimum for a better size. Though, with guinea pigs, bigger is always better!
Enclosures to Avoid!
There are many great options for your guinea pig enclosure - we even have our own selection of favourite guinea pig cages. However, it’s still incredibly common to see the small, wired cages that are nowhere near big enough for a full grown guinea pig being sold in pet stores. These are beyond smaller than the minimum for a piggy, and it’s still a shock that these stores can get away with selling them.
They are typically advertised and pushed upon those who are less knowledgeable in guinea pig care, which emphasises the importance of thorough research before buying an animal. Guinea pigs deserve the utmost love and care from us, and that starts with the home we provide for them.
