Guinea Pigs Size & Weight: How Big Do Guinea Pigs Get?

Guinea pig size and weight

Guinea pigs can be frail little animals when it comes to their health, so it’s important to routinely weigh them. But you might be wondering, what is a normal weight for a guinea pig? How can you tell if they weigh too much or too little?

Guinea pigs vary in weight, but can weigh anywhere from 900 grams to 1500 grams or more! They don’t typically get overweight so long as they’re eating a proper diet and have a large enough cage.

In this article, we’ll discuss guinea pig size and weight, how big guinea pigs get, and how to tell if your guinea pig is too fat or too thin.

Guinea Pig Size: How Big Are Guinea Pigs?

Guinea pigs typically range from 8-12 inches long. Males tend to be larger than females, and their breed makes a difference too! Very large breeds may measure as much as 18 inches, but this is uncommon.

When it comes to height, guinea pigs have short little legs and typically measure just a few inches tall.

Guinea Pig Weight: How Much Should Guinea Pigs Weigh?

Guinea pigs can vary a lot in weight (900 – 1500 grams or more) and still be perfectly healthy! While there are some loose rules–males typically weigh more than females, and some breeds are bigger than others–there are also many exceptions.

To know if a guinea pig is a healthy weight, look at their body:

  • You shouldn’t be able to see their hips, spine, or ribs–but you should be able to feel them easily. You shouldn’t, however, be able to feel each individual rib.
  • You should also be able to see their feet when viewing them from the side.
  • Their front chest area should be narrower than their rear, but not dramatically so.
  • Their tummy should appear straight and curveless while viewing them from the side, not curved upward or sagging downward.
Guinea pig with a normal weight

How to Keep Your Guinea Pig at a Healthy Weight

It’s also important to pay attention to your guinea pig’s care. Guinea pigs fed the right diet and who have room to roam are not going to be overweight and shouldn’t be put on any sort of diet.

Feeding a lot of sugary foods like fruit or carrot, excess pellets (more than ⅛ cup), or the wrong hay type (such as alfalfa hay) are the most common reasons a piggy may be overweight. They may also be overweight if they have a cage under 7.5 square feet for one to two pigs, or whatever the minimum is for the size of their herd.

Although there are many estimates out there for how much guinea pigs should weigh, it’s often dangerous to try and make your guinea pig fit the mold. Guinea Lynx notes that even many veterinary books cite weights that are abnormal for pet guinea pigs.

The most important thing is to learn what’s normal for your individual piggy and to keep an eye on their weight from there. Gradual weight gain as a baby guinea pig ages is normal, while weight loss at any age can indicate a health problem unless it’s due to a purposeful change you made, such as decreasing pellets.

Senior guinea pigs may lose weight as they age, but should always see a vet if they lose 50 grams or more in a single week.

How Much Do Baby Guinea Pigs Weigh?

Most baby guinea pigs will start at just 60-120 grams, and can gain 50 grams or more each week for their first eight weeks. After this, their weight will continue to grow until they reach their full size at around one year old.

Just like with adults, baby guinea pigs don’t have specific weight criteria and some perfectly healthy piggies will fall outside the normal weight range. The most important thing is to weigh them regularly and ensure they’re gaining weight at a steady pace.

Baby guinea pigs can grow very quickly, so don’t be alarmed if they gain a lot of weight at first. This should even out once they’re fully grown, and they should maintain their adult weight fairly steadily.

If your baby guinea pig loses weight or you think they’re growing too slowly, see your veterinarian as this can be a sign of illness.

How Much Should a Pregnant Guinea Pig Weigh?

Pregnant guinea pig weight

Pregnant guinea pigs can as much as double in weight. However, there’s no specific weight your guinea pig should be at any point in her pregnancy. Instead, focus on ensuring she’s gradually gaining weight. 

If your guinea pig is pregnant, please see your veterinarian for guidance and to ensure a healthy pregnancy for both mama and her babies.

Guinea pigs over six months old experiencing their first pregnancy are very likely to die giving birth naturally, so seeking veterinary care is vital in these cases. Your guinea pig will likely need a c-section.

Do Male or Female Guinea Pigs Weigh More?

Generally, male guinea pigs weigh more than females. However, this won’t always be the case for your piggies. Some females are heftier than normal, and some boys are smaller.

How Often Should I Weigh My Guinea Pigs?

Some people weigh their guinea pigs once weekly, while others weigh them monthly. There is some debate here, but I prefer weekly.

My reasoning is that weight loss is often the first sign of illness, and illness in guinea pigs can progress very quickly. A weekly weigh-in makes you more likely to catch health problems so you can act on them right away.

If your guinea pig is sick or recovering from illness or surgery, weigh them daily until they recover. They’re in a frailer state than usual, and checking their weight daily helps ensure that they’re eating.

How to Weigh Your Guinea Pig

  • Purchase a kitchen scale. You want the scale to measure in grams for the most accurate results.
  • Find a container large enough for your guinea pig to fit inside and set it on the scale. This will help to contain them while they’re being weighed.
  • Tare the scale. There’s typically a “tare” button that will set the weight to zero while the container is on it. This ensures you’re only getting the weight of your guinea pig without the added weight of your container.
  • Set your piggy in the container and record their weight. You might have to wait a minute for them to stop moving, or repeatedly tuck their feet back into the container if they try to run off.
  • Keep note of their weight in a notebook or on your phone. I prefer a spreadsheet on my phone for this, but anywhere will do! You just want to be able to compare their weights from week to week.
  • Repeat for additional guinea pigs.

Your guinea pig’s weight will fluctuate naturally throughout the day. For the most accurate results, choose one place to weigh your guinea pigs and try to weigh them at the same time each week.

For instance, don’t weigh your guinea pig after veggie time one week and before veggies the next, because they’ll be heavier after eating!

If your guinea pig loses 50 grams or more, see your veterinarian as this can be a sign of illness. Weight loss of 100 grams or more over a single week warrants an emergency vet trip.

Biggest and Smallest Guinea Pig Breeds

Rex guinea pigs tend to be the largest pet guinea pigs, while Texels and Americans are two of the smallest.

There are also Cuy guinea pigs, which are much larger than your typical pet guinea pig. Sadly, this is because they’re bred as meat in some parts of the world. 

Some people keep Cuys as pets, but they tend to be more wild in nature than other domestic piggies. They also have shorter lifespans.

Chunky guinea pig

How Do I Know if My Guinea Pig is Too Fat?

There are two ways to determine if your guinea pig is overweight:

  • Looking at their care, and
  • Assessing the shape of their body

It’s important to remember that guinea pigs need to eat constantly and have fast metabolisms. They also tend to lose weight quickly when ill, so it’s better for them to be a little chunky than underweight.

If your guinea pig is overweight, please make sure they aren’t pregnant! Pregnant piggies need more food than usual, and you and your vet will need to have a watchful eye on them to ensure a healthy pregnancy.

Feeding and Housing

Guinea pigs are unlikely to be overweight when fed a proper diet and given enough space in their cage. Remember that piggies have fast metabolisms and need to eat constantly to survive.

Never limit hay, and don’t decrease their overall veggie intake to under one cup per guinea pig. Instead, focus on feeding the right variety of vegetables–mostly dark, leafy greens with limited “treats” such as carrots and fruit.

Free-feeding pellets is the most common way guinea pigs can become overweight. Make sure you’re feeding just ⅛ cup of high-quality, timothy-based pellets to your guinea pig. Avoid pellets with seeds or colorful pieces as these are unhealthy and often contain harmful ingredients.

For two guinea pigs, the minimum cage size is 7.5 square feet–but 10.5 square feet or more gives them much more room to run around. Even with floor time, guinea pigs in small cages can’t get the exercise they need.

Body Score

On an overweight guinea pig, it’ll be difficult to feel their spine, hips, and ribs. Their belly will have an outward curve as it hangs down in a “u” shape, and in very overweight piggies it may touch the ground. It may also be difficult to see their feet.

The rear and front ends may be the same size or close, while the chest area is slimmer in guinea pigs at a healthy weight.

Long-haired piggies can be more difficult to assess, but do make sure to factor in their long fur! They may look like they weigh more than they do.

Plump guinea pig

How Do I Know if My Guinea Pig is Too Thin?

Firstly, remember that weight loss warrants a vet trip as soon as possible! While senior piggies may naturally weigh less than they did in young adulthood, weight loss is often an indicator of illness.

If your guinea pig is skinny because they’ve stopped eating, this warrants an emergency vet visit. They can go into GI Stasis, which is deadly, in just 6-8 hours.

If your guinea pig hasn’t lost weight, but you’re worried they’re too skinny, look for the following:

  • Visible ribs, spine, or hip bones
  • Their front half is much smaller than their rear end, or their front and rear are the same size and both are very thin
  • Their stomach curves inward toward the body when viewed from the side

You’ll also want to ensure your piggy is getting a proper diet, which we’ll discuss below.


Guinea pigs should always have unlimited access to fresh timothy hay (or another acceptable hay such as orchard grass).

Hay makes up 80% of their diet, and they are constantly eating in order to keep their weight up and survive. Not having access to hay even for a few hours can be dangerous.

You’ll also want to ensure your guinea pig is eating a cup of mixed vegetables, which should consist mainly of dark, leafy greens.

Lastly, ⅛ cup of pellets will ensure your piggy gets all of their daily nutrients. While some people feed unlimited vegetables instead, this requires a lot of research and dedication to get right–it isn’t for inexperienced piggy owners!

Helping Your Guinea Pig Gain Weight

If you’re already feeding all of the above and your guinea pig is still underweight, the first step is to see your veterinarian. There is likely a medical reason they’re not gaining or keeping on weight.

Feeding more pellets can help sick or senior piggies keep their weight up. You can also feed a supplement such as Oxbow Critical Care. This is mixed with water to turn into a paste, which can then be put into a bowl or syringe fed.

Oat hay is higher in fat and can be fed alongside your regular hay, or you can add a healthy forage mix to their hay to encourage them to eat it.

Thank you for reading! I hope this article has answered all of your questions about guinea pig size and weight, and how to tell if your guinea pig is a healthy weight.

Remember to talk to your veterinarian if you suspect your guinea pig isn’t healthy. Never limit their hay intake and be sure to feed a variety of dark, leafy greens daily.

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *