Originally Posted by RegularGuy
Grade = vertical gain / horizontal distance
Your horizontal distance of .7 mile = 3696 ft
345 ft of gain / 3696 ft = .09334... or approximately 9/100ths which is a 9% grade.
That is my understanding of how it is calculated. By the way, a 9% grade is respectably steep and not that common. I believe state routes have to be 7% or less and generally interstate highways are even less.