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Guinea Pigs Full Size | Your questions answered

The article will discuss what to expect a guinea pigs full size to be. 

How big are Guinea Pigs full size?

Adult Guinea Pigs full size (Cavia Porcellus) range on average from 8-12 inches (20-30 cm) in length and weigh right around 1.5-2.6 lbs (700-1200 g). 

The guinea pig is the largest rodent that is a typical family pet.

To put it more precisely, full-grown guinea pig males weigh between 2.1 to 2.6 lbs (950-1200 g) and female Guinea Pigs 1.5-1.8 lbs (700-850 g).

The most popular breeds of Guinea Pigs include the American Guinea Pig, Rex guinea pig, Abyssinian Guinea Pig, and the Teddy Guinea Pigs. 

The guinea pig size will vary some within the breed. 

The American Cavy Breeders Association only recognizes 13 breeds within North America, while the British Cavy Council recognizes 50 varieties. 

The smallest being the common pet Guinea Pig, the American. And the largest being the Rex.

guinea pig full size with long hair
Photo credit- Canva

How big is a newborn Guinea Pig?

A baby Guinea Pig is born approximately 3-4 oz (85-115 g) and roughly 3 inches (8 cm) in length. 

The Cavy will continue to nurse on their mother until they are approximately three weeks old and 6 oz (170 g) in weight. 

Then, it is that time to wean from their mother and start eating solid food like their parents.

How big are the pet store Guinea Pigs?

National stores such as Petco and Petsmart offer these popular pets for sale on the floor and several other rodents such as Rats, Hamsters, and Gerbils. 

The Guinea Pigs will come fully grown, between 1.5-2.6 lbs depending on the sex. 

One can pick up all the associated supplies included, including but not limited to a cage, vitamin C supplements, hay, bedding, pellets for food, water bottle, etc.

For comparison: How big is a wild Guinea Pig from South America?

The Brazilian Guinea Pig is very similar in size and length to the domesticated Guinea Pig. 

A wild Guinea Pigs adult will weigh 1.1-1.8 lbs (500-800 g) and 7.5-13 inches (19-33 cm) in length. 

The lighter frame will indicate the active nature of being in the wild, in contrast to the sedentary lifestyle of the domestic Guinea Pigs.

small guinea pig
Photo credit- Canva

What month are Guinea Pigs considered adults?

Young Guinea Pigs grow rapidly for the first 14 weeks of life; they grow almost to their adult size by this time.

 After 14 weeks, the Cavy will be putting on weight to round out their adult form but not growing in length or height.

When you get your new pet, you should monitor their health by how much they eat and poop.

 A Guinea Pig is an adult at six months of age. At this point, the Guinea will need to be monitored for unnecessary weight gain. 

To properly take care of your Guinea Pig, obtaining a kitchen scale to weigh them weekly will be necessary to help ward off obesity.

Then one can intervene and correct the amount of food given before it is too late, and a diet will be necessary. 

What is the average lifespan of a guinea pig?

The average lifespan of a guinea pig is around 5-8 years of age.

How do you maintain a safe weight in a Guinea Pig? What do you feed them to keep them at a safe weight?

As pet owners, it’s essential to learn all you can to keep your guinea pig at a healthy weight. 

To get a Cavy to a healthy weight, they need a proper diet and supplementation with Vitamin C. 

When discussing a Guinea Pig’s diet, the first thing to think about is what this animal needs to survive and thrive. 

Once they are thriving, one can focus on spending the next 5-8 years as your special companion.

Hay is the cornerstone of a Guinea Pig diet; they require approximately 70-80% of the diet to be strictly derived from hay. 

The variety of hay that works best with the GI tract is grass hay.

If you use the wrong type of hay, it can cause health problems, so it’s important to know the different types.

What are some hay varieties for guinea pigs?

Grass Hay is low in calcium, protein, and high fiber. Varieties include Timothy, Oat, and Orchard grass.

Alfalfa Hay is high in calcium, protein, and calories which is only suitable for growing Cavies or pregnant/nursing mothers. An increase in calories and nutrition helps them grow and heal. While serving alfalfa hay to adults will lead to kidney stones and should only be used sparingly.

 Timothy Hay is the most common hay for Guinea Pigs. It will be the most readily available at pet stores and nutritionally significant.

An important note here is that Guinea Pigs form their dietary choices early in life, and such are picky eaters for the rest of their lives. 

Knowing what the prior owner/shop fed the Guinea Pig will be important to continue the same nutritional lifestyle.

After hay- pellets and fresh food round out the diet.

Pellets are a commercially produced product that combines Timothy Hay with essential vitamins and minerals specially formulated for the Guineas.

Think of these pellets like a multi-vitamin they take daily.

The usual serving is 1/8 of a cup of pellets daily, but it should be adjusted if your specific Guinea Pig is over or underweight.

Fresh food rounds out the complete diet of the Cavy, and such food you will need to monitor.

Providing too much fresh food will lead to diarrhea. Weight gain will occur if provided too much as well. 

If the fresh food is not eaten within a couple of hours, the food should be taken away and not provided again that day.

guinea pig full size eating a carrot
Photo Credit- Canva

What are some fresh vegetables guinea pigs can eat?

  • bell peppers
  • leaf lettuce like romaine
  • parsley
  •  live wheat grass
  • carrot tops
  •  celery leaves
  •  clover
  •  spinach
  • green alfalfa
  • pesticide free dandelion leaves.

Vegetables belonging to the cruciferous family, including broccoli, cauliflower, and cabbage, should be avoided for daily use as they may cause stomach upset. 

Fruits should be considered a treat and provided sparingly (every 2-3 days) and in minimal amounts. 

Some but not limited to appropriate fruits include;

  •  grapes
  • citrus fruits
  • apples

Vitamin C supplementation is an essential part of a Cavies lifestyle. Being unable to synthesize their vitamin C within the body, they need to obtain it from food or supplement sources. 

Pellets contain vitamin C but will break down over time, so more is recommended to prevent Scurvy in your pet.

 Over-the-counter Vitamin C can be purchased at a pet store or even at the grocery store in liquid or tab form. 

How much vitamin C does a guinea pig need?

They need between 10-25 mg per 2.2 lbs, or 1 kg daily.

Finally, water is the last ingredient to round out a healthy guinea pig diet for these popular household pets. 

Fresh water via a sipper in water bottles outside the cage is the easiest to manage as there is no chance of large spills within the enclosure. 

Providing fresh water daily will ensure that your guinea pig is well hydrated and free of dehydration.

Want to learn more about guinea pigs? Check out these articles!

For information on sources check out our reference page.