Cat Years – How Old is my Cat in Human Years

As cats’ lifespan is significantly shorter compared to humans’, people frequently love to equate cat years with human years. Anecdotally, you may have heard the so-called ‘7-year rule’ that is, every cat year is equal to about 7 human years.

This is biologically incorrect, however. In actuality, there’s no real scientific way to calculate the relationship between human and cat years. However, there are general guidelines that you can use if you really want to conceive your cat’s age from a perspective that you can better understand and empathize with.

The Guidelines

The general rule of thumb is that the first 2 years of a cat’s life are roughly equivalent to the first 20-25 years of a person and then, each subsequent year after is about another 4-5 human years.

The reason for this irregular conversion rate is that the developmental growth of cats is much greater during their first two years of life than anytime afterward. They go from a neonatal kitten to a fully-formed and developed adult in that time, versus a person who takes more than 20 years for this to occur.

  • Early Development

Humans have long gestation periods and child-rearing phases. Domestic cats only go through a gestation period of 52 – 74 days.

After giving birth, kittens can be separated from their mothers as young as 2 months or at most, 10 – 12 weeks of attention and care. After being separated from their mothers as they’ve passed their “toddler years”, they go on to be almost fully independent by 3 or 4 months.

That is why some foster homes wouldn’t let their kittens to be adopted unless they are at least 10-weeks-old. Therefore, kittens which are around 3 – 6 months should be equally developed as a child around 4 – 8 years of age.

Further, the kittens’ critical socialization period is before they are 6 months of age. Whereas for humans, this development continues until the age of 5 or more.

  • Cat Puberty

Unspayed female cats or queens start menstruating or come into heat as early as 4 – 6 months. At this stage, they are considered able enough to get pregnant. However, on average, 8 – 10 months are the healthiest times for them to have a litter.

On the other hand, male cats or tomcats are able to impregnate once they reach 6-months-old and some can be fathers to litters as early as 10-months-old.

In comparison, an average female child reaches puberty as early as 9-years-old to as late as 15-years-old, while boys reach sexual maturity between 12 and 14 years of age.

  • Maturity and Old Age

On average, cats that have reached the age of 10 – 12 years are considered senior cat-izens. They show signs of aging the same way humans do like developing eye and knee problems.

But not everything is noticeable to the naked eye. Their internal organs may deteriorate over time like developing certain cancers; while some develop high blood pressure and heart problems which are something you can only detect with the help of a vet.

However, this doesn’t mean that all cats are old when they reach these ages. Some cats may show signs of aging earlier than others while some will stay practically healthy until after they reach the age of 12.

Comparison: Cat Years vs. Human Years

Here are some other general age benchmarks comparing cat years to humans:

  • A 1-year old cat is around 15
  • A 5-year-old cat is around 35
  • A 10-year-old cat is around 55
  • A 15-year-old cat would be close to 80 years old in human years
  • The average lifespan of a cat is around 16 years, but it is not uncommon for cats to survive into their 20s

Keep in mind that these conversions generally correspond to the rate of aging for an indoor cat. Some sources suggest outdoor cats may functionally age at a rate of almost twice as fast compared to an indoor animal.

This is because outdoor or free-roaming cats, especially in urban areas, are susceptible to a number of dangers that risk them to injury or even death. These include vehicular accidents, attacks from other animals – either domestic or wild, injury from other humans, poison, and diseases from the environment.

Framing cat years in human years, although not a very exact science, is important for putting perspective on the animal’s life for the owner. If one year for an adult cat equals five for us, then, you can see how illnesses can develop or how organ functions can decrease in animals at a seemingly escalated rate.

This also helps illustrate why at a minimum, yearly vet visits are so important. In general, this helps frame what each life stage means for a cat to us. A 1-year old cat is a fully-developed adult and by this time, that cat will have established full personality, preferences, and even baseline health parameters.

 By the time a cat is between 3 and 6 years old, chronic and/or congenital health concerns may need to start being addressed. At this time, you can catch problems before they become more serious and you can start supplements, for example, to support your cat’s well-being.

Once cats are around 9 years old, they are considered seniors. Check-ups should be done more frequently at this point and bloodwork should be taken to be compared to previous medical history as changes can occur quickly at this stage.

ageing cat

Stray or Adopted Cats - How Old are They?

If you have a cat that was a stray, adopted from a shelter or otherwise, has an unknown history and background, there are a few ways that a vet can use to determine how old the animal is; although this is still approximate.

Teeth are usually the main indicator of age as a cat’s teeth have a pretty stereotypical change over time. For cats under a year old, the presence and development of particular teeth are key, as we have a very good understanding of what teeth come out at what times.

Furthermore, for older cats, staining, tartar build-up, and other damage which is very typical for cats usually occur at consistent rates. For senior cats though, only an age range may be discernible with this method.

Muscle tone, coat health, and eye appearance are all other physical indicators that can be used to determine the age. For example, as cats get older, they lose muscle tone, get thicker hair, as well as display areas of greyness. Surprisingly, senior cats also will sometimes have a jagged iris upon inspection!

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