When kittens are born they weigh approximately between 80 and 100 grams. Kittens from (semi)feral moms can weigh a bit less. They are born with their eyes closed and deaf. The umbilical cord stays attached to the belly for a few days, until it falls of around day 3- 5.
The eyes open between 7 and 14 days, most often around day 10 after birth. At this time they can also hear. Even with eyes open the kittens don’t see very well yet. It takes at least till week 8 for them to start seeing everything sharp.
At 3 weeks they start moving around a bit more. Attempts to walk are made and playing with littermates starts.
Teeth start to appear between 3 and 4 weeks of age. Up to this point the kittens only drink with their mom. From 4 weeks on they will start to try and eat solid food and drink water.
At 5 weeks they are able to walk quite well and usually are able to eat solid food. They groom themselves and use a litter pan if offered.
At 6 weeks the eyes start to get their definitive color. All kittens start with blue eyes, but from 6 weeks onward they gradually change into green or yellow variants.
Weight gain should be around 70-100 grams per week. Meaning a newborn kitten starts at 100 grams and at 6 weeks should weigh approximately 600 grams.
From 6 weeks on it gets a bit harder to estimate age of a kitten. They still grow at approx. 100 grams a week. But there are no such characteristic milestones as the umbilical cord, eyes opening and eyes changing color.
At about 4 months they start changing baby teeth for adult ones. You probably won’t notice this as the expelled teeth are often swallowed during meals.
Kittens can be weaned from their mother at 9 weeks, but preferably at 12 weeks of age. The bond between mother and child is very strong. Given the chance they will nurse from their mother until they are 6 months!
Early weaning may cause behavioral issues .