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Cat Years vs Human Years: Comparisons & FAQ

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By Nicole Cosgrove

ginger cat with the owner

You’re probably familiar with the saying that a year of a cat’s life is equal to 7 human years. While this is a good average to help us understand the significant difference in how our cats age in comparison, it’s not entirely accurate.

Cats actually age much faster than humans, which is important for understanding their learning, development, and health status at different milestones. Let’s take a look at how they compare.

Overview of Cat Years

age of cat in human years
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We usually understand animal age in terms of “human years,” which is a simple calculation. Unlike dogs, which have an average based on size and breed, cats are standard across the board.

According to the American Animal Hospital Association, a cat’s lifespan is as follows:

  • The first year of a cat’s life is approximately 15 human years.
  • The second year of a cat’s life is about another 9 years.
  • Past the second year, each year of a cat’s life is approximately 4 human years.

So, a 3-year-old cat is roughly 28 in human years.

How Do Cats Age?

three cute kittens on the grass
Image Credit: yanikap, Shutterstock

Now that we understand how cats age, the “1 year equals 7 human years” isn’t entirely accurate. Cats experience much of their aging as a kitten, then the aging process slows down. For example, 1 month of a kitten’s life is approximately equal to 1 year of a human’s life.

The process gradually speeds up, with each month equaling more human years. At 18 months, a young cat is 21 human years—fully an adult!

So, how did the American Animal Hospital Association come up with these averages? They’re based on the physical and behavioral changes that take place at different stages, which are similar milestones in a human’s life.

It’s not exact, so your cat may age slower or faster than these averages in some respects. But unlike dogs, which vary significantly between size and breed, cat breeds don’t have much variation in how they age across breeds or sizes.

What Impacts Cat Aging?

Naturally, cats that have chronic medical conditions may age differently than healthy cats, but another significant factor in how a cat ages is whether they’re indoor or outdoor cats.

Indoor cats are generally safe from predators, disease, exposure to the elements, or starvation and thirst. These cats are less likely to experience stress and trauma or encounter infectious diseases, so they typically have longer lifespans.

Outdoor cats are exposed to greater risk from predators, the elements, and infectious diseases, which can shorten their lifespan. They do have a more enriched environment that challenges them and tests their natural instincts, however, which may be missing for indoor cats.

grey persian cat in garden
Image Credit: Cattrall, Shutterstock
  • Faster maturity and development
  • No social or cultural influence on aging
  • Shorter lifespan

Overview of Human Years

Human years are the way we understand the aging process. One year of life equals one year of growing up or aging, and we understand important physical or psychological milestones like adulthood at 18 years old, the legal drinking age at 21, and 30 as the age at which we enter into mature adulthood. Our senior years are typically 65 and older.

In addition to identifiable physical and behavioral changes that mark different human life stages, we also have social and economic factors that are considered appropriate or typical. Cultural and social influences impact our perception of the right age for sexual relationships, marriage, parenthood, moving out of our parents’ homes, and more.

grey cat with baby
Image Credit: aprilante, Shutterstock

How Do Humans Age?

Aging is a construct that includes biological, psychological, physiological, behavioral, and social changes. We are born prematurely in the sense that we are entirely dependent on our mothers for a long period of time and require a lot of nurturing.

We eventually grow into independence over time, whether physical or social. Babies develop to hold their heads up on their own, crawl, and walk. Eventually, we can function independently and learn to feed ourselves and handle our own personal care.

As we move into the adolescent and teen years, we develop into maturity. Physically, we go through puberty and reach biological sexual maturity, and then growth stops. Emotionally and socially, we develop more independence and control, our personalities and preferences flourish, and we lay the foundation for who we will become.

Our period of maturity progresses incrementally until we reach middle adulthood. While we may still learn and develop our personalities and social skills, this period typically includes physical changes like chronic health conditions, food and diet sensitivities, and the negative effects of stress. Middle-aged people may experience mental health concerns like a fear of mortality or depression and loss as parents age or pass away, children grow into adults and begin a life of their own.

In our senior years, or a period that is near or surpassing the life expectancy of human beings, we begin to see an increase in sickness, injury, disease, physical aging, and cognitive decline. This is more of a cultural life stage than a biological one, and the effects of “old age” can vary significantly between individuals.

What Impacts Human Aging?

people in the park
Image Credit: Piqsels

All humans will follow the same general aging process, but a lot of factors determine how quickly we age. Physical aging progresses faster in people with substance abuse or high stress levels, as well as in people who spend a lot of time in the sun.

Genetics play a role in human aging as well. Children can have diseases typically seen in middle-aged or old adults, such as cancers or heart conditions. That said, a younger person has a generally better chance at rebounding from a serious condition than an older, vulnerable person.

Lifestyle habits can have a significant effect on the aging process. Diet, exercise, sleep habits, socialization, and continued learning all have a positive impact on the aging process.

  • Longer lifespan
  • More control over the aging process
  • Slower maturity
  • Social and cultural perceptions of aging


While cats and humans follow the same general aging process of infancy into adulthood and old age, the life stages in between and speed of aging vary significantly. Cats are equivalent to a full human adult of legal drinking age by 18 months, while we’re still babies and heavily dependent on our mothers at that stage. Of course, this also means that cats need special attention as seniors when they reach 10 or 11 years, which is still a child in human years.

Understanding these differences in our perception of the aging process in ourselves and our cats helps us appreciate a cat’s life stages and understand how to support them throughout their whole lives.

Featured Image Credit: Yuriy Seleznev, Shutterstock

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