(Found this when I was trying to document for someone that total elevation gain for a ride is a good measure of difficulty).


* 0% grade is exactly flat (and a negative grade, less then zero, is downhill).

* 2% grade does not seem very steep, but it's enough to substantially reduce forward speed, and for most riders it will absorb more than half their power output.

* 6% grade is enough to cut speed to well under half, and absorb more than 80% of a rider's power output (leaving less than 20% to fight air resistance and rolling friction).

* 10% grade, and anyone who is not a fit and frequent rider is off their bike walking -- and anyone who is not a racer is reaching for all the extra power they've got.

(Hmmm, they didn't go up to 22%!! Well, I know I can ride 7% for several miles, but it isn't pretty, and I'm riding at 4mph, which is about a quarter of my average speed!!)