how do you figure grades

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having come back from pennsylvania and riding the mountians i am wondering how they figure grades and what they mean. i rode on 8% and being from michigan have never been beatin down so fast.

having come back from pennsylvania and riding the mountians i am wondering how they figure grades and what they mean. i rode on 8% and being from michigan have never been beatin down so fast.
8 % grade means for every 12-and-a-half feet of run their is one foot of rise.

10% means that for every ten feet you go forward you go up one foot. In England they would call a 10% grade a one in ten.

A 5 % grade takes you up one foot for every 20 feet or forward travel; this would be a one in twenty.

A one in five is what you do not want.