You can always compare the IV of two options, on the same underlying, in order to have a good idea of their relative price and try to cook up a reasonable spread where the option(s) you sell has a higher IV than the one(s) you buy. However, AFAIK, you can't compute the IV of different spreads (more than 1 leg) and enter (buy) the one with the lowest IV. If I am mistaken about that, I would like a reference. So are there any recognized methods of ranking spreads from cheap to expensive? TIA.