Remember also that it will depend on the size of the front rings too. The "compact double" on a cross bike is not necessarily the same that you might find on a road bike. Typical for a road bike is a 50 x 34, cross bikes often have a 36 x 46. (triples on cross bikes are usually smaller too 28x38x48)

Like Indy said - plug the stats into a gear inch calculator to get a much better picture.