How Big Do Guinea Pigs Get?

Guinea pigs (Cavia porcellus) belong to the Caviidae family and are classified traditionally as New World hystricomorph rodents that are closely related to capybaras, porcupines, and chinchillas. Guinea pigs, also called cavies, are herbivores that are native to the Andes mountains and surrounding areas of South America, where they inhabit grassy plains, rocky areas, and marshes. Wild cavies are highly social and form small herds. They do not dig their own burrows but instead rely on dense, thorny vegetation for cover or inhabit abandoned burrows of other animals.

Guinea pigs were domesticated between 5,000 and 7,000 years ago as a sustainable food source, and for medicinal and spiritual purposes. They were introduced to Europe in the 16th century by returning traders and were introduced to North America primarily in the early to mid-1800s, arriving via Europe as part of the exotic pet trade and becoming popular household pets by the early 20th century. Beyond their winning personalities, the guinea pigs’ continued popularity lies in their compact size. Although different breeds are of different sizes, no cavies would be considered large. Continue reading to discover how big guinea pigs get.

How Large Do Guinea Pigs Get?

Guinea pig pups are precocial, meaning they are mobile and can eat solid food at birth, although they nurse for their first few weeks of life. Pups grow quickly, often doubling their weight within the first month. Female pups (sows) can reach maturity as early as 4–6 weeks, while males (boars) mature around 8 weeks. Once guinea pigs are three months old, their growth slows considerably, although they will continue to grow at a slower, steadier rate until they reach their full adult size, typically between 6 and 12 months.

The average adult guinea pig measures 8 to 10 inches in length and weighs between 1.5 and 2.6 pounds.

What is the Largest Guinea pig Breed?

There are 13 confirmed breeds of guinea pigs, according to the Journal of Entomology and Zoology Studies.

The rex cavy is the largest recognized breed of guinea pig. They can be up to 18 inches long and weigh as much as 3 pounds, though most adults are smaller. Rex cavies are known for their calm, friendly temperament, large droopy ears, and low-maintenance fur.

Diet and Care

A guinea pig is most likely to reach its fullest potential size when provided with a diet of unlimited high-quality hay (timothy, orchard), a daily allowance of fortified pellets, and fresh vitamin-C-rich vegetables. Guinea pigs under 6 months old require alfalfa for added calcium. Along with a healthful diet, guinea pigs thrive with spacious, comfortable accommodations and daily exercise.
Overfeeding, excessive treats, and a lack of exercise can cause guinea pigs to become overweight or even obese. Obese guinea pigs may have difficulty grooming and face serious health risks such as heart disease, diabetes, and bumblefoot, a condition in which their feet become inflamed, infected, or ulcerated due to excessive pressure from their extra weight.