How Big Does a Guinea Pig Get?

A guinea pig’s size can vary based on age, gender, breed, and diet. It’s important to know their average weight so that you can monitor their diet effectively.

In turn, you can make sure your pet stays healthy at all times.

This article provides an overview of the different sizes a guinea pig can be. In addition to that, it offers other information that is related to their size.

Factors that Affect the Size of Guinea Pigs

In addition to the details in this piece, it’s always a good idea to consult your veterinarian about your guinea pig’s size.

They can give you accurate numbers that are ideal for your pet.

Thus, these sizes are simply averages that can help you know more about these animals. It can also help you to determine if you can comfortably keep a guinea in your home.

So, based on the size of the animal, you’ll know what size cage or hutch you should get.

Age of the Guinea Pig

Age is the most significant factor that affects the size of guinea pigs.

Below are some average lengths and weights of differently aged guinea pigs.

Size Based on Length

You can measure your guinea pig’s length to determine its size. The length varies based on the animal’s age. So, here’s what you should know.

  • A newborn guinea pig is about 3 to 4 inches long (8 to 10 centimeters)
  • An 8-week-old guinea pig is about 6 to 8 inches long (15 to 20 centimeters)
  • A 16-week-old guinea pig is about 8 to 10 inches long (20 to 25 centimeters)
  • A 14-months old guinea pig is about 8 to 12 inches long (20 to 30 centimeters)

The length of the guinea pig can vary based on gender and breed as well.

Size Based on Weight

In addition to its length, you can also measure the size of your guinea pig based on its weight.

Here are some averages of their size (based on weight).

  • A 2-week-old guinea pig is about 0.3 to 0.5 pounds (150 to 250 grams)
  • A 4-week-old guinea pig is about 0.6 to 0.9 pounds (285 to 400 grams)
  • A 6-week-old guinea pig is about 0.8 to 1.2 pounds (350 to 550 grams)
  • An 8-week-old guinea pig is about 0.9 to 1.5 pounds (400 to 700 grams)
  • A 10-week-old guinea pig is about 1.1 to 1.8 pounds (500 to 800 grams)
  • A 12-week-old guinea pig is about 1.2 to 1.8 pounds (550 to 900 grams)
  • A 14-week-old guinea pig is about 1.3 to 2.0 pounds (600 to 950 grams)

On the other hand, a fully grown guinea pig (14 months) is about 1.5 to 2.6 pounds (700 to 1200 grams).

Guinea pigs typically reach adulthood by 6 months.

By 14 weeks of age, they stop growing significantly.

However, typically, they completely stop growing after the age of 14 months.

So, don’t be alarmed if your pet grows longer or heavier during adulthood.

The Gender of the Guinea Pig

The gender of guinea pigs also affects their size and weight.

Typically, male guinea pigs of the same age and breed are heavier and longer than their female counterparts.

The size difference is mostly consistent at different ages of the animal.

So, male guinea pig pups and adults are always larger than female pups and adults.

The difference in weight between male and female guinea pig adults is about 0.2 pounds or 100 grams. That said, the difference may vary based on breed and health.

The Breed of the Guinea Pig

There are various guinea pig breeds, and some of them are larger than others.

That said, breed-related information can be inaccurate due to cross-breeding.

It’s best to consult your vet about your pet’s breed details.

The Mother Guinea Pig’s Litter Size

In many cases, the size of the mother guinea pig’s litter can affect the length of the pups at birth.

So, pups born in relatively small litters will be smaller than those born in larger ones.

The Diet of the Guinea Pig

An important factor that affects the size of a guinea pig is its diet. This is one factor that you have direct control over for your pet.

A diet with minimal fiber can cause your pet to put on fat.

Overfeeding it can also cause it to gain weight, which may make it thicker from the sides.

Thus, it’s always best to feed your guinea pig high-quality food that’s made for it specifically.

Avoid feeding it food for rabbits or other small animals.

It can help to consult your vet or pet store for diet information.

Why It’s Important to Monitor Your Pet Guinea Pig’s Size

It’s important to make it a regular practice to monitor your pet guinea pig’s size.

Guinea pigs’ lifespan can decrease significantly due to being overweight.

You Can Help Prevent a Guinea Pig from Developing Health Problems

Guinea pigs can have various health problems, including heart disease, high blood pressure, cystitis, arthritis, and more.

Therefore, by monitoring the weight and size, you can adjust your pet’s diet and consult your vet for immediate action.

In turn, you can help it return to a healthy size sooner than later.

Consistently measuring weight and size can help prevent health problems from developing in the first place.

Overweight May or May Not Linked With Health Problems

In some cases, an underlying condition can result in a guinea pig’s increase in weight and size.

Thus, a vet can perform the necessary tests and diagnose a condition (if present).

As a result, your pet can begin its recovery.

When there’s no underlying condition, lifestyle and diet changes most likely will be necessary.

Increasing its exercise and activity may be vital.

In some cases, small cages prevent guinea pigs from getting adequate physical activity to stay fit.

How to Determine Your Guinea Pigs Size and Weight

There are a few ways to determine the size and weight of your guinea pig at home.

As a result, you won’t have to rely on getting that information during vet visits only. Here’s what you must know.

Measuring Your Guinea Pig’s Length

You can measure your guinea pig’s length from its nose tip to its rear. Measuring your guinea pig can be challenging because it most likely won’t stay still.

You must place a measuring tape or ruler beside its body while it’s standing on a flat surface.

The measuring tape should be parallel to your pet’s body.

You simply need to get a rough estimate of its length. Accuracy is not necessary.

Measuring Your Guinea Pig’s Weight

You can check if your guinea pig is overweight by simply feeling its body.

It may not be as accurate as using a measuring scale, but it’s good enough for monitoring your pet’s health daily.

Your guinea pig is at its ideal weight if you can’t feel its ribs individually when you hold it.

The ribs should not be prominent, but you should be able to tell that they’re there.

On the other hand, your guinea pig may be underweight if you can feel each rib individually.

In addition to that, its spine and hips shouldn’t be visible. That said, you should be able to feel them.

Moreover, the guinea pig’s chest should be narrowing than its hind. It also shouldn’t have any abdominal curve.

You can also look for signs of it being overweight or obese by looking at it.

Your guinea pig may be overweight if its belly touches the floor when it’s standing upright. Also, the feet may not be visible.

Don’t Try to Touch Your Guinea Pig If It Doesn’t Like to Be Touched or Handled

Some guinea pigs may not like being handled. In that case, you may not be able to use this method.

It’s important that you don’t try to touch it if it seems uncomfortable. You may scare or stress the animal.

Consider Using a Measuring Scale

You could use a measuring scale to measure your guinea pig’s weight if you want an accurate result. Any kitchen scale will suffice.

So, you can place a small bowl that’s large enough to fit your guinea pig. Place it onto the scale, and note down the weight of the bowl.

You can also add a small pillow to keep your pet comfortable.

Measure the weight of the pillow, too, if you’re using one. Next, place your guinea pig into the bowl and note down the weight.

The purpose of the bowl is to have your piggy stay in place.

Subtract the weight of the bowl (and pillow) from the measurement with the guinea pig.

Thus, you’ll have the exact weight of your guinea pig.

Last Few Words

As a pet owner, it’s critical that you keep a close eye on your guinea pig’s size and weight.

Sudden changes can be linked with underlying health conditions. Visit your vet immediately in that case.

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