How to age your cat like a pro: How to tell how old a kitten is

If you adopted your cat or kitten from a shelter or friend, or even if you found him or her outside you may not know…

If you adopted your cat or kitten from a shelter or friend, or even if you found him or her outside you may not know exactly how old they are. In that case, you need some physical clues to help you determine how to tell a kitten’s age.

In this mini-guide, we will show you how to age your cat to try and get as close to their real age as possible.

There are several things you look for when aging your cat

Physical Characteristics to look for
Teeth This is by far one of the easiest and most common methods to age an adult cat. Kittens are not born with teeth and they also go through a stage of having baby teeth. They usually have all of their adult teeth by 6 months of age, which makes it easy to tell if you have a kitten younger than 6 months (Read how to age your cat by looking at their teeth)
Weight Kittens gain weight quickly, but weight is often used to help determine the age when they are younger than 6 months. As a rule of thumb, kittens usually gain about a pound a month the first four months of their lives and then their weights tend to increase rapidly for a couple of months until they reach their adult size. (Read about aging cats by their weight)
FurAs cats age their fur changes. Kittens are usually born with soft but thick fur and it thins out as they become adults. (Read about how cat‘s fur change as they get older)
Playfulness Kittens are extremely playful and this usually decreases as they get older (Read more about cats and their activity levels)
EyesCats go through many changes with their eyes as they age. Kittens are born with their eyes closed which open over the first couple of weeks of life, they can also change color once open. Middle to senior-aged cats may also go through ocular changes that include cataracts and nuclear sclerosis. (Read about how to tell the age of a cat by their eyes)
Hormones Cats usually have their first heat at 6 months, if you have a kitten that has not had her first heat or started spraying (marking) if you have a male cat they are most likely still fairly young. (Read about how cats and their heat can help you age them)
Claws(Read more about aging cats by their claws)

You should always keep in mind that any age you get is always going to be a guesstimate, even your vet is giving you her best guess.

1. Teeth


One of the easiest ways to tell a kitten’s age is to look at their teeth

Kittens are born without teeth, just like human babies. They usually get their first teeth around 3 weeks of age, however, some may get them earlier or later.

These first set of teeth are deciduous or ‘baby teeth’ that will fall out and be replaced by a full set of adult teeth.

A kitten’s deciduous teeth are extremely small, pointy, and sharp.

Most kittens will have 26 deciduous teeth by the age of four months, at this time they usually start falling out and are replaced by their permanent or adult teeth. As their teeth are erupting you may notice some teething at this time. Most kittens will have all of their permanent teeth by the age of six months.

  • The first adult teeth to come in are the middle incisors at around 14 weeks
  • The second and third incisors follow at about 15 and 16 weeks
  • Pre-Molars and Canines 16-20 Weeks of age


Adult cats have 30 permanent or adult teeth.

Once a cat has their adult teeth it becomes a bit more difficult to age them because they don’t have the common markers of tooth growth that kittens do. But you can still get fairly close to their actual age by looking at the amount of tartar on their teeth.

Keep in mind that this will be a best guess or ‘guesstimate’ as it’s commonly called.

As your cat ages, they will tend to accumulate plaque on their teeth, and by the time they reach two years of age their teeth may be yellow from plaque. As they age the plaque hardents and becomes tartar as it builds up on the teeth.

Tartar continues to build up over the years and you may notice that there is a thick layer of dental calculus on the teeth, especially on the gum line of the canine teeth.


Senior or elderly cats may also begin to lose teeth, have teeth that are chipped and worn, or develop gum disease. This is commonly seen between 8-10 years of age.

When aging a cat by the amount of tartar or plaque on their teeth keep in mind that this varies depending on some factors:

  • Home care: If a cat is receiving excellent home care including regular teeth brushing they may have less tartar than one that has never had their teeth brushed
  • Diet: If a cat is eating dry food they tend to have less tartar than one that is eating dry food. The wet food can easily cling to the teeth and cause tartar to build up faster whereas dry food may actually help prevent tartar as it has been said that it can help to scrape some of the build-up from the teeth.
  • Dental cleanings: If owners are taking their cat to the vet regularly for dental cleanings and one is not, cats of the same age will obviously have totally different tartar or plaque build-up issues.
  • Inside vs Outside cats: Indoor cats are a lot more sheltered and do not have to defend themselves as much as an outdoor cat may have to which can lead to things like chipped or missing teeth long before they reach mid-life or senior ages. In addition, outdoor cats are usually eating without much discretion so they may have a bit more plaque or tartar build-up.
0-2 WeeksNo teeth at this time
3 WeeksStart seeing teeth erupt
16 WeeksShould have all decidious teeth
26 WeeksDecidious teeth begin falling out and replaced with adult teeth
6 MonthsShould have all adult teeth
2 YearsStart to notice mild plaque build-up and yellowing of the teeth
5 Years Teeth may be totally yellow and there may be some tartar build-up at gums
10 Years & UpSevere tartar and may have gum disease, teeth may be missing or chipped
Cat and teeth growth | @thepetsdigest

2. Weight

Kittens grow extremely fast and reach maturity in what seems to be a blink of the eye.

One rule of thumb to keep in mind is that many of the gain about one pound a month for the first four months and then reach about 80% of their adult size at about 6 or 7 months.

By the time they are 9-10 months, most cats will be at their adult weight.

4 Weeks1 pound
8 Weeks2 pounds
12 Weeks3 pounds
16 Weeks4 pounds

Weights vary depending on a few factors including

  • Diet: Of course, cats that are fed high-fat, high-carbohydrate diets will pick up weight a lot faster than one that is on a more nutritious diet
  • Breed: Some breeds will grow a lot larger than others like Maine Coons which have been known to reach almost 20 pounds
  • Activity: Inactivity can cause weight gain but since most kittens are pretty active this doesn’t usually become an issue until they get older

3. Eyes

Kittens are born with their eyes closed, and they don’t open until about 10 days of age, but this can occur anywhere between 2 and 15 days of age.

Also, all kittens are born with blue eyes!

2-15 DaysEyes open
14 DaysPupils dialate
21 DaysBegin to focus on things
8 WeeksGet their true eye color

As cats age, they may have occurences that help dictate their age like the presene of cataracts and nucler sclerosis.

4. Activity Level

At around 3 weeks of age is when kittens start to walk but with a pretty uncoordinated gait.

At four to five weeks they begin to walk steadily and begin being a lot more playful and mischevious.

Most kittens continue to be fairly playful well into the year mark but as they get older you may notice them slow down quite a bit and opt for relaxing on the couch instead of running laps around the house.

5. Fur

Another thing that can help when aging kittens and cats is to look at the fur.

Most kitten fur will be soft, thick, and short as opposed to many adult cats.

Adult cat’s fur will usually become silkier and grow to their predetermined genetic legth of short, medium, or long. Kittens will get their adult fur at around 6-8 months of age.

As your cat gets older you may notice some changes to the fur like graying or a bit more coarsness. In addition, some cats may not groom themselves as well as they once did which can lead to more matting.

6. Hormones

You can be fairly sure that your cat is under 6 months if they have not had a heat yet for females or started to mark for males.

7. Claws

As newborns kittens can not retract their claws until about 4 weeks old.