It's kind of misleading to rate a ride by average grade. You might be riding up a gradual slope forever and then dropping off a cliff for 200 feet. Or vice-versa would be really tough! It doesn't take many 20% grades to wipe me out, no matter how short they are. Grade is meant to measure the steepness of a particular hill, or specifically a piece of road that may not be the full hill. If you want to know how much climbing you do on a ride, just take the total vertical feet, possibly with a max grade thrown in. BTW you can measure grade by laying your smart phone on the pavement. There's an app for that!