How to Determine Kitten Age
Less than one week old: (3-7 oz) Eyes shut, ears flat to head, skin looks pink. Part of umbilical cord may still be attached.
One-two weeks: (8-11 oz) Eyes and ears beginning to open and kittens will move around but usually spend their time eating and sleeping.
Three weeks: (7.5-14.5 oz) Eyes open and focusing. Ears are open and standing up. Kitten will start to respond to noises and movement. The first wobbly steps are taken and baby teeth start to come in.
Four-five weeks: (8-16.75 oz) Running, playing, digging, and pouncing occur often. Kittens will start to wean and will be able to lap up formula, eat soft food, and use the litter box by themselves. Eye color starting to change.
Six-seven weeks: (1-1.5 lbs) Kittens are quite active, fully weaned and using litter box. Eye color changes from blue to its permanent color. Usually friendly and very playful at this stage, wrestling with littermates.
Eight weeks: (2 lbs) Kittens look like little versions of full grown cats.
Kitten Age Photos (courtesy of Alley Cat Allies)