Since the grades are subjective, and largely determined by the first ascentionists, (although through consensus sometimes re-graded) this is not possible. My subjective take on it, up to 5.11+, can't speak for anything beyond that, is that a bump in a grade, any grade is about the same increase in difficulty. My climbing has mostly been in Joshua Tree, Idyllwild, Smith Rocks and a bit in the valley.