How often do you want to do laundry? Also, if you cloth diaper for awhile (my son is 16 months), the elastic will start to go on some diapers and you may have some that delaminate. So I always end up adding to my stash (plus I'm a total CD addict!). If you want to do laundry every other day, and you have a newborn, I'd say you'd need 30 to be safe. It also depends on what kind you're using. If you use inserts with covers, you can get by with fewer covers and more inserts. But it's always good to start with a good variety of types (all in ones, all in twos, fitteds, hybrids) to see what you'll like.