If u normally wear a 34 and u want the same look displayed above (that's 16CM) u need a 35 probably. If u get a 33 they WILL NOT fit. Trust me on that.
Don't buy offline. You need to go in a store, Barney's carries them in every location. Certain cuts mean you need to wear a diff size. Ex: I wear 32 in 16CM and 17CM but I wear 30 in 18CM.