There are correct sizes available for diapers for newborns, as well as regular disposable diapers. It is important to refer to these as otherwise, you run the risk of the diapers slipping off or you could be left dealing with some diaper leaks, which are always inconvenient to deal with, especially in public. The available sizes for disposable diapers range from newborn to size 6, and size 6 diapers are perfect for kids that weigh more than 35 lbs. Newborn diapers are ideal for if your baby is 10 lbs. Or lighter. If your baby is anywhere between 8 and 15 lbs., the disposable diapers to go for would be size 1 or 2. And then there are size 3 diapers, which are perfect for babies that are 16 to 28 lbs. In weight. For babies that are around 22 to 37 lbs. In weight, size 4 disposable diapers are best. For over 27 lbs., choose size 5.