Comparing Sizes: How Big Do Guinea Pigs Get?
How big do guinea pigs get? From Abyssian guinea pigs to Rex guinea pigs, some guinea pigs are bigger than others. What size is considered to be adult when guinea pig proportions can vary so widely?
Some guinea pigs get pretty large, but their breeding age and environment can also affect their size and weight. Aside from breed, only length and weight are the standards guinea pigs are sized by. There’s no “one size fits all” answer to these questions, but here are some helpful guidelines for choosing the right size guinea pig (with tons of personality) for your family.
How Big Is the Average Guinea Pig?
How big do guinea pigs get? The average guinea pig weighs 25-40 ounces with a length of 8-10 inches.
However, male guinea pigs tend to weigh a third more than female guinea pigs. A female guinea pig usually weighs up to two pounds, while a male guinea pig weighs between two and 2.6 pounds. A guinea pig's tail can be just one inch long and isn’t usually seen.
Large and Small Guinea Pig Breeds
The American Cavy Breeders Association (ACBA) currently identifies 13 guinea pig breeds. However, there are other breeds the association doesn’t recognize. Below, you’ll learn about the various breeds of guinea pigs and just how big they can grow.
Large Guinea Pig Breeds
What is the largest guinea pig out there? Eight million years ago, the biggest guinea pig that ever lived weighed 1,543 pounds and was 1.4 yards tall. Scientists call this guinea pig the Phoberomys pattersoni, and it lived in northern Venezuela.
Today, the largest guinea reaches under two feet in length. The Rex guinea pig can grow up to 17 inches when it’s an adult! Known as a gentle giant, this lap guinea pig adores affection.
Generally, larger-size guinea pigs grow from ten to twelve inches. Abyssian, Cornet, Himalayan, Lunkarya, Peruvian, Ridgeback, Sheba, Teddy and Texel breeds can all grow up to twelve inches.
Small Guinea Pig Breeds
Some of the breeds that can be considered large are also considered to be small, such as the Ridgeback. It depends on the size a guinea pig reaches at maturity. Guinea pigs don’t come in “dwarf” sizes, according to ACBA. However, some breeders do breed guinea pigs too young, and the resulting pups may be smaller than usual. A good determinant is the size of the litter. If the litter is large, then the pups will tend to be smaller at maturity.
Guinea Pig Sizes by Maturity
How big do guinea pigs get? In just eight weeks, baby guinea pigs double in size and weight. In just another eight weeks, they do it again! Once a pup is just over a year old, it’s considered to have reached maturity. Below is a brief age and size chart:
| Age | Size |
| Birth | 3-4 inches |
| 8 weeks | 6-8 inches |
| 16 weeks | 8-10 inches |
| 14 months | 8-12 inches |
How do you tell if a guinea pig is a male (boar) or female (sow)? Wait until it’s at least three weeks old to search for gender differences.
What Size Should Your Guinea Pig Cage Be?
When choosing a guinea pig cage, you should make your selection based on the size your guinea pig will reach at maturity.
The figures offered here are only approximations, but this guide should get you started. All cavies vary in size, but if yours seems too small or too big, you should consult a veterinarian.
Guinea pigs have sweet temperaments and are a good size pet to start young children with, but families should note a guinea pig’s home has its own needs, too. The environment should contain room to roam, plenty of grass, an outside-the-cage play space, and separate spaces for water, food, bathroom and nesting. Guinea pigs don’t tend to get stuck or lost, and with the right care, are perfectly happy at home with you.