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How Big Do Guinea Pigs Get? Size & Growth Chart

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By Nicole Cosgrove

close up of a guinea pig

If you are considering adopting a young guinea pig, you may be wondering: how big will it get? What is the average size of an adult cavy?

Like most pets, the size of an adult will depend on its breed, gender, and genetics, among other factors. Generally, adult guinea pigs are about 5 inches tall and measure 10 to 12 inches in length. The typical weight range is between 1.5 and 3 pounds.

Guinea pigs reach full physical maturity at 16 weeks, after which they stop growing. Understanding the ideal size of an adult allows you to track if your cavy is following a healthy growth pattern.

Read on to find out more about how big guinea pigs get. We will share a detailed growth and weight chart and discuss factors that may affect the size of an individual pet.

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Guinea Pig Overview

Guinea pigs are active, so providing appropriate environmental enrichment is crucial. Start by offering foraging opportunities by adding ample amounts of untreated wicker baskets filled with hay within the enclosure.

Guinea pigs are social and love being handled by their human companions. When you place one hand inside the cage, your furry friend will quickly approach you, signifying it wants a petting or cuddling session.

Compared to other small rodents, guinea pigs are relatively long-lived. They have an average lifespan of five to seven years. Pets that receive proper care tend to live longer.

Guinea Pig Size and Growth Chart

Guinea pigs can weigh between 1.5 and 3 pounds depending on breed and gender. They are short, with relatively longer bodies measuring between 10 and 12 inches. Although the length of your pet will highly depend on its genetics, its weight is often lifestyle related and can have implications on its overall health.

Here is a general guinea pig size chart to help you determine whether your furry friend is growing as expected.

Age Weight Range
2 to 4 weeks 0.55 to 0.62 Pounds (250 to 285 grams)
6 to 8 weeks 0.77 to 1.2 pounds (350 to 550 grams)
10 to 12 weeks 1.4 to 2 pounds (650 to 950 grams)
14 to 16 weeks 1.5 to 3 pounds (680 to 1360 grams)
silkie guinea pig
Image Credit: Linn Currie, Shutterstock

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When Does a Guinea Pig Stop Growing?

Guinea pigs are physiologically mature at 16 weeks (4 months), after which they stop growing. Although they may add a few grams before they become full adults at 24 weeks (6 months), the difference is relatively minute. Also, you’ll notice that they don’t increase in length after the 16 weeks mark.

Cavies reach sexual maturity earlier before they are physiologically mature.

Males are sexually mature and ready to mate at two to three months of age. Females are typically sexually mature at two months and begin having fertile periods. If you decide not to have your pets spayed or neutered, you must separate males and females to prevent unwanted pregnancies.

guinea pig side view
Image Credit: Katya36, Pixabay

3 Factors Affecting the Size of a Guinea Pig

Numerous aspects play a fundamental role in determining how big cavies get. Among those factors are the litter size and degree of nourishment a guinea pig receives before birth.

Typically, small litters produce bigger babies that quickly increase in length and weight. This can have a minor effect on the size of a cavy before it stops growing at 16 weeks.

Here are the three factors that can significantly impact your pet’s size.

1. Breed

One of the primary factors that will influence the adult size of your guinea pig is its breed. For instance, Rex guinea pigs are giants in their world, reaching up to 18 inches in length and weighing a whopping three pounds.

On the other hand, the American guinea pig is relatively tiny and measures a mere eight to nine inches in length with a weight of 1.5 to 2.5 pounds.

guinea pig and flowers
Image Credit: Miroslav Hlavko, Shutterstock

2. Gender

Male guinea pigs are slightly larger than their female counterparts. Boars weigh 2 to 3 pounds, while sows weigh 1.5 to 2.6 pounds. Although both genders measure 8 and 10 inches while fully mature, the weight difference between males and females is often noticeable.


3. Genetics

Sometimes, even cavies of the same breed differ in size because of their genetics. For instance, if the parents are slightly shorter than their peers, there is a good chance that babies from their litter will also have the short gene.

On the other hand, breeding two considerably large guinea pigs will likely ensure a litter of bigger babies.

Guinea Pig
Image Credit: chiprida, Pixabay

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Ideal Diet for Maintaining a Healthy Weight

Guinea pigs, like most rodent pets, love hay. They need an unlimited supply of top-quality hay for good digestive health and to wear down their teeth. Provide the hay in small portions throughout the day and remove the old stuff your pet did not eat.

Also, remember to provide plenty of fresh water to keep your furry friend hydrated.

The ideal daily diet should consist of at least 80% hay. The remaining 20% of the diet should consist of fresh vegetables, fruits, and moderated quantities of dry pellets.

cute guinea pig eating hay
Image Credit: Thiago Janoni, Shutterstock

How to Measure Your Guinea Pig

Measuring guinea pigs can be challenging because they never stop moving. Although they are cuddly, popping them on a scale and ensuring they remain still can be a problem.

Here are a few steps that can make your work easier.

Gather the Necessary Supplies

The first step is to gather the tools you need to measure the weight and length of your cavies. Here is what you need.

  • Weighing scale (a baking scale will do)
  • Tape measure
  • Small box

Weigh the Pet

It is essential to make your piggy feel safe and secure. Place the weighing scale on a flat, steady surface and place your small box on top. Take readings of the box’s weight and gently drop your pet inside it. The container should stop it from hopping off too fast.

Take the readings and deduct the weight of the box. Voila! Now you can tell how much your pet weighs.

It is crucial to keep track of your guinea pig’s weight consistently. Ensure you write down your readings on a spreadsheet and add the data each time you weigh your pet. This way, you can tell if there are any drastic changes in its overall size.

Measure the Piggy’s Length

The height of guinea pigs is not a vital metric for knowing how big it is. However, you must measure their length to ensure they have hit the expected milestone.

To measure your piggy, place it on a flat surface and place your tape measure or ruler next to it and parallel to its body. Take the readings and note them down on your spreadsheet.

Red Abyssinian Guinea Pig on green grass
Image Credit: Tettania, Shutterstock

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Final Thoughts

Guinea pigs vary in size, and it’s important to know what proportions to expect of your pet based on its breed and gender. Generally, weight and size are important indicators of overall health. For instance, you can tell your pet is unwell if it cannot conceal its weight loss.

Obesity can also be a cause for alarm.

Cavies are foodies, and their big appetites can make them too sluggish to work out. If your furry friend is overweight, you must encourage more exercise to help it shed unhealthy weight. Obesity can shorten life expectancy and increase the likelihood of life-threatening health complications like heart disease and high blood pressure.

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Featured Image Credit: Miroslav Hlavko, Shutterstock

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