Guinea Pig Years to Human Years: How Old is Your Cavy in Human Years?

Guinea pig years to human years

Wondering how old your precious guinea pigs are in human years?

Our fuzzy pets have a relatively long lifespan compared to other small pets, and they stay our loyal companions through a significant part of our lives. They live 5-7 years on average, although they can live much longer if they have good genes and are well cared for!

But when do our cavies become teenagers? When can they legally go to night clubs? And when do they enter old age? Luckily, we have all the answers!

Guinea Pig Years to Human Years Chart

After scouring through the internet, I realized there wasn’t an official research paper I could use to create a guinea pig years to human years chart, like there is for rats and mice. But – after putting together rat-to-human and mice-to-human age charts based on available research for these rodent species, I figured that I could use the same methods and principles from those research papers and adjust them for guinea pigs.

So, I’ve collected all the data and put this “guinea pig years to human years” chart together. The chart takes different guinea pig life stages and compares them to human life stages. You can see the logic behind my calculations in the content below. The same logic was used in rat-to-human age and mice-to-human age research papers, so the data should be pretty reliable.

Note: while this chart should be pretty accurate in translating guinea pig years to human years, you should still only use it for informational and entertainment purposes.

Guinea pig years to human years chart
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Let’s go over different guinea pig’s life stages and how they compare to humans. Keep in mind that this is just an estimate. Like humans, some guinea pigs can mature earlier and some might be a little late to the party.

Weaning Period

Guinea pigs’ gestation lasts 59-72 days, which is longer than in other small mammals. For this reason, guinea pig babies are already well-developed when born. They are covered in fur, their eyes are open, and their teeth are already present.

When baby guinea pigs are around 3 weeks old, their mom no longer feeds them, and they eat and drink by themselves. Sometimes, they still get milk supplementation up to 4 weeks of age.

In comparison, human babies usually start eating solid food and drinking from a cup when they are around 6 months old.

Based on this, we can say that a 3-week-old guinea pig would be around 6 months old in human age.


Entering puberty or adolescence happens when guinea pigs reach sexual maturity and can start reproducing. For males, that is when they reach approximately 2-3 months. For females, it’s a bit earlier – at 2 months of age (55-70 days). However, both males and females can mature and be fertile even earlier.

According to this research, juvenile females can reach sexual maturity much earlier (at 26 days old) when they’re housed with adult males. If they’re not in the company of males, the first vaginal opening, or oestrus, which indicates they are ready to start mating usually happens later than that.

On the other hand, humans reach puberty at 11.5 years on average. Based on this, a 2-3 month-old guinea pig would be approximately 11.5 years old in human age.


Guinea pigs enter adulthood when their epiphyseal or “growth” plates start closing, which means they’ve completed most of the growing. The same goes for humans. The epiphyseal closure means the growth is finished. Both guinea pigs and humans can grow slightly after that, but most of their growth is done.

In guinea pigs, epiphyseal closure starts at 4-5 months of age (20 weeks on average), and, in that time, their growth ceases. In humans, the closure of the epiphyseal plates happens when we’re around 20 years old.

Based on this, we can consider guinea pigs adults and 20-years-olds in human age when they’re 20 weeks old (or 4-5 months).

Start of Old Age

Guinea pigs are considered old when they reach 5 (human) years.

In humans, we usually count the start of old age when women enter menopause, which is around 51 years of age.

Guinea pig life cycle

To sum it all up, here are guinea pig years vs. human years:

  • 3 weeks = 6 months
  • 2-3 months = 11.5 years
  • 4-5 months = 20 years
  • 1 year = 30 years
  • 2 years = 35 years
  • 3 years = 40 years
  • 4 years = 45 years
  • 5 years = 50 years
  • 6 years = 60 years
  • 7 years = 70 years
  • 8 years = 80 years

How old are your guinea pigs in human years?

Let us know in the comments section!


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