How To Tell A Kitten's Age? What Causes Aging? Ultimate Animal Facts!

Rajnandini Roychoudhury
Feb 29, 2024 By Rajnandini Roychoudhury
Originally Published on Nov 22, 2021
Edited by Lara Simpson
British blue kitten walking.
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Age: 3-18
Read time: 10.7 Min

Babies are one of the cutest things in existence, be it human or animal, and can get the best reactions out of people!

In terms of animals, cats are seen as among the cutest in existence. It comes to nobody's surprise that cat babies, known as kittens, are cute to the core.

In many cases, kittens are often abandoned by their mothers or left behind because of the mother's death. In these cases, kittens are adopted by humans and taken care of until they can fend for themselves. However, taking care of kittens is not as simple as it seems, and many conditions have to be followed to take care of them. One such case is determining the kitten's age so that harmful things are not introduced to them as many elements of caring depend on the age of the animal since what is well-received by an adult cat will not be the same for a kitten.

If you like this article about How to tell a kittens age? Be sure to check out articles about why do kittens bite and how often do kittens eat too!

How to tell a kitten's age by teeth?

Sometimes it is necessary to know the age of the animal you are taking care of in case its mother abandoned it or you are merely adopting or playing the role of a foster.

The age of young kittens can be tough to figure out if you do not know what you are doing; however, there are many ways that can help in figuring out how old your kitten is.

A kitten's age can easily be figured out by checking its teeth, as teeth formation can say a lot about age. In the case of a newborn kitten, it will be toothless at this point, the kitten solely depends on the mother's milk, so if there are no teeth in the mouth, the kitten is a newborn one. Bottle-fed kittens should be fed in a gap of five hours, and by now, they should be able to use a litter box individually.

In kittens, the baby teeth will start forming when they are 3-weeks-old, and the permanent teeth will develop when they are three to four months of age. Kitten teeth are tiny, making it challenging to determine if the incisors are permanent or baby teeth. Baby teeth are comparatively smaller than permanent teeth, and the baby teeth are pointed, whereas permanent teeth are wide and have a flat edge.

A more descriptive answer to this is monitoring the progress of teeth growth in your kitten as various ages have different formations.

When the kitten is 3-weeks-old, the first teeth set will start appearing. These tiny teeth will appear at the front of the mouth and are called incisors, which form through the gums.

At four weeks old, the teeth will continue to develop, and the canine teeth situated near the incisors will form through the gums.

At five weeks old, the teeth will continue developing, and the formation of the premolars can be seen. During this period, the kitten should be acquainted with kitten food in the form of wet food. This adaptation should be slow for the kitten to develop a habit of eating kitten food entirely.

At six weeks old, the kitten will develop milk or deciduous teeth and be fed wet food. The kitten needs to be taken care of at this stage, and no form of solid food should be fed to it.

At seven weeks old, the kitten will grow all of its baby teeth, and by the end of this period, the kitten should be comfortable eating wet food.

At eight weeks old, most kittens start eating individually and will become independent.

How to tell a kitten's age by weight?

The age of kittens can also be identified by maintaining a routine check of their weight as growing kittens will start gaining weight and develop into mature or juveniles slowly.

Newborn kittens weigh between 1.7-5.2 oz (50-150 g), and they should be fed through bottle feeding this time around as the kittens' eyes are closed, and they do not have any teeth to chew food with. As your kitten slowly grows, its weight will also increase.

A one-week-old kitten should double its original weight and weigh around 5.2-8.8 oz (150-250 g). A two-week-old kitten will have a body mass that ranges between 8.8-12.3 oz (250-350 g). A three-week-old kitten will weigh around 12.3-15.8 oz (350-450 g). A four-week-old kitten will start gaining weight exponentially and will weigh between 15.8-19.4 oz (450-550 g). A five-week-old kitten will weigh between 19.4-22.9 oz (550-650 g). A six-week-old kitten will weigh between 22.9-26.4 oz (650-750 g). A seven-week-old kitten will weigh between 26.4-29.9 oz (750-850 g). An eight-week-old kitten will weigh between 29.9-33.5 oz (850-950 g).

By the end of its weaning period, the kitten will weigh at least eight to nine times its birth weight, which is a great way to learn the age of your kitten.

How to tell a kitten's age by size?

The body size of a kitten is another way to figure out its age.

Kittens begin to start interacting with other cats and fight them for territories at about six months of age. Juvenile or old kittens will bite more often compared to grown cats or younger kittens.

As the kittens grow in size, their physical characteristics develop, which can help find out more about their age. The ears start to extend, and these will hold themselves up well. The short fur of the kittens will begin to grow and become medium or long.

The eye color will become much more apparent as they grow, and the presence of green, blue or yellow eyes can be clearly seen. As kittens start to look more like adults, their growth rate will slow down, and the muscle tone will develop to aid them in learning new things based on stealth.

Baby cat sleeping.

Best Way To Tell A Kitten's Age

If you are in the process of introducing your kitten to other pets, you will need to have an exact idea of the age of the kitten, as many adult cats and old kittens will show a bit of aggressive behavior towards the new kitten.

Some of the best ways to determine the age of a kitten are based on examining their physical traits; some of these practices are as follows:

If the kitten is a newborn and its eyes are closed, ears folded, it is better to examine its body, especially the stomach, to find any traces of the umbilical cord stump, as usually, the mother cat will bite it off after giving birth. If there is an umbilical cord, then your kitten is between one to three days old, as, by the end of the third day, the umbilical cord stump falls off by itself.

Examining the kitten's eyes is another method of determining its age, as newborns are born with their eyes closed and helpless during this phase. If you check the eyes and they are closed, it means that the kitten is less than a week old, as the kitten's eyes open when they are around 10-14 days of age. However, the kitten can open its eyes between seven to 10 days of age in some cases. So, all in all, if your kitten has its eyes closed, it is likely a newborn, and if the eyes are open, it is at least a week old. Remember that the natural eye color of kittens is blue by default, and as the kittens grow, the color changes to whichever color the cat will have for its lifetime.

Checking the ears is another way of determining the age as the ears develop while the kitten grows. If your kitten's ears are close to the head, it is presumably one week of age since the ear canals of baby kittens are closed on birth. It takes the ears between five to eight days to start opening. Even though the ears will begin opening up, it takes a certain amount of time for them to be completely visible. By the end of the second or third week of your kitten's life, the ears will pop up.

Keeping a check on your kitten's teeth is another great way to determine its age. The development of teeth is slow progress and can tell a lot about age. A kitten that has no teeth is a newborn or younger than two weeks of age. The presence of teeth and teeth formation and characteristics is a great way to learn more about its age.

The baby teeth usually show up when the kitten is around two to three weeks old. The first teeth set that pops up are the incisors. The canine teeth will start appearing at the age of three to four weeks. These teeth are pointed and take their place next to the incisor teeth.

Premolars will grow around four to six weeks of age, and these teeth take their place between the molar and canine set of teeth. If the molars have not developed and the baby teeth are still present, the kitten should be around four months of age. At this stage, your kitten should have 12 incisors, six at the top and six at the bottom, four canines equally divided into two at the bottom and two at the top, three premolars at the top, and two premolars at the bottom of the jaw.

If you find large teeth in your kitten's mouth, its age should be more than four months.

The formation of teeth should follow the timely routine of adult incisors appearing at four months of age. By the six-month mark, the baby teeth set of canines, molars, and premolars are replaced by adult teeth. If you find that your kitten has all the adult teeth set, complete with all four molars, then your kitten is presumably seven months of age.

Weight is also an essential factor that plays a role in determining the age of a kitten as the weight is never constant and changes with the development of the body. As aforementioned, your kitten's body mass changes with each developmental phase, and by the end of its growth spurt, your kitten will weigh seven to eight times its initial birth weight.

On average, cats will grow one pound per month from their first week till the weight steadies itself at around 10 lb (4.5 kg). So, in hindsight, a two-month-old kitten will weigh 2 lb (0.9 kg), and a six-month-old kitten cat will weigh 6 lb (2.7 kg).

The average adult weight of cats is estimated to be around 9-10 lb (4-4.5 kg) for most cats.

How to tell a young kitten's age?

The age of kittens, especially a newborn kitten, can be tough to estimate if the right conditions are not met. To safely determine the age, you should be able to notice small things that will contribute to assessing the age. The weight, body size, and formation of teeth are essential factors that can be extremely helpful in discovering age.

As we already know, kittens will be born with their eyes and ears closed, and it is never recommended to open their eyes forcefully. Blue eyes are the default color, and the colors change as the kitten grows.

In their newborn stage, kittens are entirely helpless, so they depend on the mother cat for everything.

By the age of one week, the ears will start unfolding. The eyes open completely by the end of two weeks, and the kitten will begin moving clumsily while still depending on the mother cat, and the teeth will start growing too. The kitten will start grooming itself, and baby teeth will become visible while the body mass increases.

At the age of four weeks, the kitten will become sturdy and run and pounce around. This is the age where you should be able to introduce dry food to your kittens, as most kittens this age develop enough teeth to chew food.

When the kitten reaches five weeks of age, it should have all of its front teeth and gain weight.

By the age of six, the kitten should be able to use the litter box and eat cat food while still being close to its mother or human raising it.

Seven weeks of age is when the kitten's sharp teeth emerge entirely.

The eyes of the kitten change from the default blue to adult color by the age of eight weeks. By the ninth week, old kittens start eating solid food, and their body language changes to that of adult cats.

By the end of the twelfth week, old kittens gain most of their body weight and count as adult cats.

Here at Kidadl, we have carefully created lots of interesting family-friendly facts for everyone to enjoy! If you liked our suggestions for how to tell a kittens age, then why not take a look at when do kittens calm down or when do kittens eyes change color?

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Written by Rajnandini Roychoudhury

Bachelor of Arts specializing in English, Master of Arts specializing in English

Rajnandini Roychoudhury picture

Rajnandini RoychoudhuryBachelor of Arts specializing in English, Master of Arts specializing in English

With a Master of Arts in English, Rajnandini has pursued her passion for the arts and has become an experienced content writer. She has worked with companies such as Writer's Zone and has had her writing skills recognized by publications such as The Telegraph. Rajnandini is also trilingual and enjoys various hobbies such as music, movies, travel, philanthropy, writing her blog, and reading classic British literature. 

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