Because most budgets cant afford to get a crate every time the pup grows larger, you should get an appropriate size for an adult and make it smaller with a divider (some crate manufactures make one, or you can use a piece of plywood, etc cut to size & wired in) - making sure your modifications are completely safe for the pup. Adult dogs should at least have enough room to stand up straight and somewhat stretch out when they lay down.
