It depends on age. Older kittens and younger cats seem to sleep less. Breed plays a part in it, too.
I have a couple moggies, one is 6 and 1/2 and the other is around 2 and 1/2. Both of them nap a lot, and usually together. Though the younger one, Tomas is more active. Sho lays around more.
And I have one DMH, that may be at least a ragdoll mix - he's around the same age as Tomas and never seems to stop. He also never seems to really nap, even if laying around he's awake and watching everything. If he's up, he's usually racing through the house after Tomas or a toy, trying to play with some odd object, chewing up paper/cardboard, or bothering whatever human he can. So I think he may only sleep 12 hours, max. It's like having a 7 month old kitten in the house.