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07-19-04, 07:30 AM
#1
live311
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Anyone know how to calculate the grade of a road? There's this access road I like to take sometimes that gains about 526 feet in about 1.5 miles. Do I divide the distance in feet by the elevation gain? That gave me about 15%, which feels about right (it's a nice little hill good for interval training). Are my calculations correct?
07-19-04, 07:34 AM
#2
live311
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Actually, never mind. I just found one, and I am correct. Google is your friend

07-19-04, 07:50 AM
#3
DPS3749
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Originally Posted by live311
Anyone know how to calculate the grade of a road? There's this access road I like to take sometimes that gains about 526 feet in about 1.5 miles. Do I divide the distance in feet by the elevation gain? That gave me about 15%, which feels about right (it's a nice little hill good for interval training). Are my calculations correct?
Your computations are correct.
07-19-04, 08:19 AM
#4
AndrewP
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Your have the calculation the wrong way around. It should be height gained divided by distance travelled times 100. In this case 526/7920*100=6.64%. I find that hills always seem steeper than they actually are, but that is just because I am an out of shape old fart - I can only climb a 15% hill for about 100 ft gain before I am poofed.
07-19-04, 09:05 AM
#5
ExMachina
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Yup, around 6.6% *average* gradient--that website is wrong.
07-19-04, 09:42 AM
#6

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Originally Posted by ExMachina
Yup, around 6.6% *average* gradient--that website is wrong.
The website expresses the gradient as a ratio.

In this case it's 1:15.05. If I assume that means one foot of elevation for every 15.05 ft of progress, that works out to (1/15.05)*100 or 6.64%

So it's not an error, just an expression of gradient different than what we are used to.
07-19-04, 10:30 AM
#7
live311
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Wow. Guess I have a long way to go before I can make it up Alpe D'Huez
08-08-07, 07:36 PM
#8
rickthebike
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Thank u

I have been tryinig to do the same thing and i had it all wrong too. Thanks for the info...I ride a road in colorado once a week called magnolia road and i have been trying to figure out the grade of that suker for a while...rick the bike....out on a ride
08-08-07, 08:57 PM
#9
deraltekluge
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To be strictly correct, it's the vertical distance divided by the horizontal distance, not the slant distance; but for the small angles you'll see on the streets, there's not much difference. Mathematically, it's the difference between the tangent of the angle and the sine of the angle. Slope in percent is the tangent of the angle multiplied by 100. An angle of 45° would rise 1 unit for every unit traveled horizontally, for a slope of 100%, but you'd travel 1.414 units along the road. A 10% slope would be 5.71° and you'd travel 1.005 units on the road for each unit horizontally. A 20% slope would be 11.31° and you'd travel 1.02 units on the road for each unit horizontally.
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