Grade Adjusted Pace estimates an equivalent pace when running on flat land. Because running up hill requires extra effort, the Grade Adjusted Pace shown will be faster than the actual pace you ran. When running down hill, the Grade Adjusted Pace will be slower than the actual pace. The steeper the grade, the larger the adjustment.
Now you can see the effort and compare hilly and flat runs more easily.
The benefit gained from running down a hill is only about half as much as the extra effort spent running up the same hill.
The calculation of Grade Adjusted Pace was inspired by work done by C.T.M. Davies studying environmental effects on running.