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 08-28-08, 05:01 AM #1 5kdad Senior Member Thread Starter     Join Date: Dec 2006 Location: Northwest Arkansas Bikes: Felt Z100 road bike and Schwinn Frontier Posts: 382 Mentioned: 1 Post(s) Tagged: 0 Thread(s) Quoted: 14 Post(s) Determining % Grade of a Hill I read about people climbing 8%, 10%, etc. grades of hills. What type of device do you use to measure a grade? Or is that info posted on a road sign?
 08-28-08, 05:31 AM #2 BlueDevil Senior Member   Join Date: Jul 2003 Location: Where the wild things are Bikes: Posts: 259 Mentioned: 3 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) My bike computer has an altimeter, and states the road grade (Though it always seems to be lower than what either road signs, or calculating off a topo map). As alluded to, you can also get a good idea of average grade on a hill by looking at a topo map. Just use: (Top Elevation(feet) - Bottom Elevation(feet)) / length of climb (feet) So if the top elevation was 800', the bottom was 200', and the climb was 1 mile, you'd use: (800-200)/5280 = 0.114, or about an 11 1/2% grade Edit- you dont have to use feet, just consistent units. e.g.- everything could be calculated in meters. Last edited by BlueDevil; 08-28-08 at 05:35 AM.
 08-28-08, 05:40 AM #3 HandsomeRyan Pants are for suckaz     Join Date: Mar 2007 Location: Mt. Airy, MD Bikes: Hardtail MTB, Fixed gear, and Commuter bike Posts: 2,578 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) As mentioned above the formula is: Elevation Gain / Length of Hill = % Grade.
 08-28-08, 06:29 AM #4 KevinF Keep on climbing   Join Date: Apr 2004 Location: Marlborough, Massachusetts Bikes: 2004 Calfee Tetra Pro Posts: 2,178 Mentioned: 1 Post(s) Tagged: 0 Thread(s) Quoted: 20 Post(s) There are multiple ways of doing it... Some cycling computers have an elevation feature. A GPS will tell you the grade as well. You can use a topo-map and figure it out by hand (rise * 100 / run). There are various websites that have elevation data (mapmyride.com, amoung others). Or you can do what I'm pretty sure most BikeForums members do -- make something up so that your story sounds better. Edit: note, if you want to be accurate, the best way of doing so is to look at the US Geological Survery topographic maps. Sometimes there will be road signs (especially on major highways) warning truckers about the % grade that's coming up. That sign usually refers to the steepest part of the upcoming downhill -- i.e., if you see "8% for next 5 miles" it means somewhere in the next 5 miles is an 8% grade, not that the next 5 miles is an unending 8% grade.
 08-28-08, 09:24 AM #5 deraltekluge Senior Member     Join Date: Sep 2006 Bikes: Kona Cinder Cone, Sun EZ-3 AX Posts: 1,195 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) To be really precise, the percentage figure is 100 * (elevation change) / (horizontal distance) = % slope For small angles of slope, there's not much difference between using horizontal distance and using distance traveled, though. It's the difference between the tangent of the angle and the sine of the angle.
 08-29-08, 07:33 PM #6 NottPhast_Phred MouthBreather/HillBonker     Join Date: Feb 2006 Bikes: Trek 7.3fx Posts: 9 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) This item could tell % grade - whatever part of the hill anyway when you check the "inclinometer:" http://westernbikeworks.com/productdetail.asp?p=STSMI Last edited by NottPhast_Phred; 08-29-08 at 07:36 PM. Reason: Photo no upload
 08-30-08, 08:54 AM #7 cc_rider Calamari to go     Join Date: May 2005 Location: Falls Church, VA Bikes: Trek 750 Posts: 3,109 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) ^^^ I've use the Sky Mounti for a couple of years. Works well for actual grade at any given point, but it doesn't give you the average grade of the whole hill.
 08-30-08, 02:29 PM #8 StephenH Uber Goober     Join Date: Sep 2007 Location: Dallas area, Texas Bikes: Posts: 11,476 Mentioned: 2 Post(s) Tagged: 0 Thread(s) Quoted: 85 Post(s) I wanted to check the ramp going down to a bridge on the bike path, and used a 2' level plus tape measure. Come to think of it, that way, you are measuring horizontal distance, not distance traveled. __________________ "be careful this rando stuff is addictive and dan's the 'pusher'."
 09-02-08, 10:04 AM #9 Garfield Cat Senior Member     Join Date: Oct 2004 Location: Huntington Beach, CA Bikes: Cervelo Prodigy Posts: 6,412 Mentioned: 2 Post(s) Tagged: 0 Thread(s) Quoted: 148 Post(s) I don't know how accurate Google Earth is, but it does measure elevation and distance.
 09-02-08, 10:22 AM #10 rm -rf don't try this at home.     Join Date: Jan 2006 Location: N. KY Bikes: Posts: 4,399 Mentioned: 5 Post(s) Tagged: 0 Thread(s) Quoted: 355 Post(s) Google Earth does estimate elevations in between known points. It'll show a pond draped down the side of a hill, for instance. I've ridden hills that were measured with the local government's mapping software. It's pretty easy to estimate grades within a few percent after riding various example known grades.

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