Bringing home a kitten doesn't always mean you'll know the kitten's birth date. Sometimes kittens that are adopted from shelters, found as strays, or received through means other than a breeder may have no known exact age.
Determining a Kitten's Age by Development
The best way to figure out the age of a kitten is to look at its physical and behavioral development. There are clear "milestones" that can be found in a kitten's growth that may not help you pin down the exact day of the birth but should help you figure out the likely week of their birth.
Kitten Eye Development
A kitten's eyes are a good indicator of their age.
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A kitten's eyes are shut when they are born and remain so until about 7 to 10 days of age.
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Note that there is often a difference between short hair and longhair cats regarding opening the eyes. Shorthair kittens tend to begin opening them sooner than longhair kittens who will tend to open them toward the end of the average time range.
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At 10 to 14 days, the kitten's eyes will be mostly open when they're awake, and they will be a brilliant bright blue.
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Once a kitten reaches two to three weeks of age, their eyes will be open like a normal adult cat when awake.
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A kitten's eyes will start to change color between three and eight weeks of age with their final color settled by three months of age. Even a kitten that will have blue eyes as an adult will show some color and shading changes to settle on their final adult hue.
Kitten Ear Development
Another clear indicator for early kitten development and age is watching their ears.
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A kitten's ears are shut completely when they are born and remain so for the first two weeks. They will appear to lay flat against the kitten's head.
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Ears begin opening after two weeks have passed and they should be fully open and erect by the time they reach three weeks of age.
Kitten Dental Development
The growth of a kitten's teeth is also a good way to determine age.
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Kittens do not have teeth when they are newborns and remain toothless until about three weeks of age.
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Deciduous and canine teeth can be visible in the mouth during the age of three to five weeks.
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The lower molars will also become visible around four to five weeks and the upper molars around eight weeks.
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A kitten will display a full set of baby teeth during the period of five to eight weeks of age.
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During the two to four-month-old time frame, the kitten's deciduous teeth will start to fall out to make room for their adult teeth.
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A kitten's set of adult teeth will be visible and set between four to seven months of age.
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If you need help to determine which are their baby and adult teeth during this period, as a guide baby teeth are tiny and pointed whereas adult teeth will look less needle-like and are thicker.
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A veterinarian can also review the level of growth to give you a narrower age range for your kitten between the four and seven-month period.
Kitten Behavioral Development
Watching how a kitten interacts with their environment, assuming the kitten is healthy, can also give you clues to their age.
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Kittens spend about 90% of their time sleeping for the first two weeks and only are awake to eat and maybe crawl around a bit on the mother.
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When a kitten reaches two to three weeks of age, they will start to move more and begin attempting to walk.
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Kittens will begin purring around three weeks of age.
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At four to five weeks of age, a kitten will start to become much more active and will play more with other kittens.
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Kittens will also start using the litter box at four to five weeks of age.
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Around six to seven weeks of age, the kittens will become more confident and start venturing away from the mother and interacting with their surroundings.
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At about seven to eight weeks of age the kittens will be weaned from the mother.
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Between eight and 16 weeks, the kittens should be actively engaging with the world and appear energetic, alert and inquisitive.
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Another indicator of age is sexual maturity. A female kitten can go into heat from the age of five months old and a male kitten can be responsive to females in heat at about the same time period.
Determining a Kitten's Age by Weight
Another common method is to weigh the kitten. Realize that weights of kittens will vary by breed, so if you have a larger breed like a Maine Coon or a smaller breed like a Siamese, their weights will be a bit different from the averages listed here. It's a good idea to use the weight method in conjunction with looking at physical and behavioral characteristics, especially if you don't know the breed and their eventual average adult weight.
| Kitten Weight by Age | |
| Age |
Average Weight |
| Up to a week old |
Up to 4 ounces |
| 7 to 10 days old |
4 to 6 ounces |
| 10 to 14 days old |
6 to 8 ounces |
| 14 to 21 days old (two to three weeks) |
8 to 12 ounces |
| 28 to 35 days old (four to five weeks) |
12 to 16 ounces |
| 42 to 49 days old (six to seven weeks) |
1 to 1-½ pounds |
| 56 days (eight weeks) |
1-½ to 2 pounds |
After eight weeks of age, a kitten will gain about one pound per month, so an average-size three-month-old kitten would be about three pounds, a four-month-old about four pounds, and so on.
Figuring Out Your Kitten's Age
It's important to determine your kitten's age to make sure you're giving them the proper health care and fulfilling their dietary needs. The best way to determine their age is to use a combination of these methods to come up with an estimate. Don't forget to bring your new feline friend in for his or her first veterinary visit and ask your veterinarian for help with deciding on your kitten's age.
