You can go by that rule, or the rule of weight, or the rule of beginner...
It's easier to ride a slightly shorter board as a beginner. Say a board that's 157cm meets your chin, you may want to try a 153cm as your first board.
I'm a tall guy and went with a 164cm as my first board, and for my second board I stepped down into a 161 because I wanted something slightly shorter. People say a shorter board can be more fun, but you need length for riding deep stuff so it kinda depends on where you ride also.
And with your name, I'm assuming your going to buy a banana? My advice is to explore other options and don't just fall into the giant marketing strategy that is the banana boards. Sure they make good boards, but they're not the only board company out there. It seems like everyone is riding a dam banana and it's rather sickening to see so many sheep on the same stick.
Are all good board companies.
Good luck and don't put to much thought in dialing your length in perfectly as you will love snowboarding as long as your board is within a handful of the recommended CM's.