so the equation is this: Elevation rise divided by horizontal distance times 100 equals percent of grade. So a short section of the ride may have a 5 foot rise in elevation over a 20 foot horizontal stretch which is a 40% grade ((5/20)*100). However if that is the ONLY elevation change over a 100 foot section of road, then the average grade is 5% ((5/100)*100). So overall most sections are measured at the begining and at the end of the hill to get total elevation gain and horizontal distance, ignoring the little localized steep stretches. The little localized steep sections though are the ones that always hurt the most. Just sayin....