When substituting hops (both varieties and pellet/plug/whole)in a recipe, I would like to keep IBU as close to the recipe target as possible. However, the best utilization chart I can find is in "Designing Great Beers" (Ray Daniels) and it requires you to know the 60 minute boil utilization of your hop variety.
Is anyone aware of a resource that provides either these 60 minute boil utilizations or enough information to complete the IBU calculation?
Also, how much variance is there in utilization for a particular variety. Obviously, the AA can be quite different for the same hop, but I am interested in how consistent utilization during boil is (for an arbitrary amount of time in boil.)