Originally Posted by Tom Stormcrowe
Smple slope formula rise/run ex: 100 feet rise an 250 feet distance is steep!
100ft/250ft=0.4 or a 40% Grade, a cliff with a vertical drop is undefined grade because you can't divide by 0, and a 7% grade = 7ft rise in 100 feet traveled
+1 explanation. I'd add that a 100% grade is a 45-degree angle, for reference.