Can you explain the percentages used to measure the slope in the road?

Question

For example, when you're climbing up a hill on your bike, 20% is a ridiculously steep, almost impossible hill. But, what does 20% resultsin as far as angles are concerned?

Does a 50% grade a 45 degree angle? And what are some of the steepest possible pitches that you might climb on a road bike?

Answer 1

You are incorrect. An 8% grade is a drop of 8 feet for every 100 traveled. TO convert the % to angle, change the % to decimal (0.08) and then take the Atan (Atan 0.08 = 4.6 degrees)

So a 50% grade is 50 feet down for every 100 traveled or 26 degrees. The steepest I have seen are 35% grade...INSANE hills.

Answer 2

It's a vector equation, and if you've ever taken trig or calculus you know what I'm talking about.

Basically, the percentage is how much elevation you gain per distance traveled. A 45 degree slope climbs as much as the distance it covers, so that would be a 100% slope.

Since a mile is 5280', a 10% grade climbs 528' per mile. The steepest I've been on is a short patch of 22%, in the middle of a climb called The Wall at the Royal Gorge in Colorado. The Wall climbs almost 1000' in a little over a mile, and it's brutal. Even in your smallest gear, 22% feels like someone is pulling you backwards with each pedal stroke.

Answer 3

No a 50% would not be a 45 deg angle - never seen one of these. The triangle would have a bottom length of 100' and a height of 50', A 100% grade would be a 45 deg.

% grade is defined in civil engineering (and what is posted on the signs) as the number of feet you go up or down in 100 ft of roadway.

I know somone already got that right, but I wanted to restate that for you since there was some disagreement and I am 100% sure as I work with this everyday.

Answer 4

In my book a 50% grade is a 45 degree angle. don't let anyone tell you different.

Answer 5

The percentage = the tangent of the angle