You could calculate the value of rise/run for a million spots on the hill, add 'em up and divide by a million, or you could just divide the total elevation gain by the total distance of the hill (close enough to the "run" for any purposes).

Figure out the elevation gain, from a garmin, polar, etc.

Figure out the length of the hill.

take the square root of legnth^2-elevation^2, this is the horizontal distance from where you started to where you finished.

Now take the arc-tangent of elevation gain over horizontal distance and you have your grade in %

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Jonathan Blyer,
ACME Bicycle Co., Brooklyn, NY

Click on http://www.gmap-pedometer.com/

Track your route to find the elevation gain/loss.

For example... say you climb is 1 mile and it gains 500 verticle feet...

Divide 500 into 5280 ft (1 mile) = Avg. Gradient 9.45%

[reply]Click on [url "http://www.gmap-pedometer.com/"]http://www.gmap-pedometer.com/[/url]

Track your route to find the elevation gain/loss.

For example... say you climb is 1 mile and it gains 500 verticle feet...

Divide 500 into 5280 ft (1 mile) = Avg. Gradient 9.45%[/reply]

Thanks, I was in Boulder and had to rent a bike so i did not have my own computer and only had my Garmin so I was curious what the average gradient of my ride was. For some reason my Garmin had perfect readings for time, distance and elevation but the gradient was out of what, considering it told me I was on a 96% gradient for about a mile!

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Proud Founder of the Jamis Mafia- Daring to be different.

That's the angle, not the grade...

wow, there are a lot of geeks on this forum! I like it!! :D

Yeah, you're right. So don't bother taking the arctangent.

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Jonathan Blyer,
ACME Bicycle Co., Brooklyn, NY

After doing a quick search, I couldn't find any websites that allow you to easily calculate gradient percentage.

I did however find this site:

http://www.dec.state.ny.us/...wildlife/beaver3.pdf

For the nuisance beaver in your life.

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Dan DeMaio
---------------------------------------------------------
Life is like riding a bicycle.
To keep your balance you must keep moving.
- Albert Einstein

I found an online calculator a couple days ago http://www.csgnetwork.com/...eclinegradecalc.html

Are you trying to figure out how your local big climb would be rated?

I was impressed to find out that the big climb in the road race I did this spring that I got dropped on might be rated a Category 2 if it was 3 miles long instead of just .3 miles ;-)

From Velonews:

One question we get quite often is how the Tour categorizes climbs. Interestingly, updated profiles of today's race show the final climb categorized as a CAT. 3 and ours shows it as a CAT. 4. That underscores the subjective element of this process, but this is a general guidline to follow throughout the Tour:

Cat . 4: Usually less than 3km in length, an easy pitch that amounts to no more than a sustained rise in the road
Cat . 3: Slightly harder, up to 5km in length
Cat . 2: Between 5km and 10km, and steeper than a 4-percent grade
Cat . 1: Long and steep. Between 10km and 20km, and steeper than a 5-percent grade.
Hors -catégorie (HC) or above category : The longest, steepest mountain climbs. Extremely difficult climbs, sometimes 15km to 20km, with grades often exceeding 10 percent.

Unless I am inputting the wrong numbers (vertical change= difference between elevation from start to finish) or the horizontal (distance from start to finish) then this calculator is wrong, as it puts a climb that I already know averages just over 9% at about 2.5%.

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______________________________________________________

Proud Founder of the Jamis Mafia- Daring to be different.

The categories are also affected depending on where they are in a given stage...

Post the numbers, and we'll tell you who is wrong. Post the road, too, and maybe someone knows it.

Horizontal distance covered is measured from the start point to a point directly under the summit on the same plane as the start point (ie the base of the triangle), not the actual road miles of the climb.

TriFold are you an engineer?

[reply]Horizontal distance covered is measured from the start point to a point directly under the summit on the same plane as the start point (ie the base of the triangle), not the actual road miles of the climb.[/reply]

So how do you calculate that differently? I usually use the milage on my Garmin training center.

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______________________________________________________

Proud Founder of the Jamis Mafia- Daring to be different.

Pythagorean Theorem...the road distance is the hypotenuse and the elevation gain is the vertical leg. Do what jonblyer said, except for the arctan part.

Many who have seen my work would answer "no".

busted!!!!!!!!!

No offense, but did you guys all fail math? All you need to know is the pythagorean theorum and the definition of grade:

Let:

x be the distance you travel along the road on your climb (the hypotenuse of the triangle)
y be the vertical gain
z be the horizontal distance travelled

So:

Grade = y/z*100

but we don't know z yet so:

x^2=y^2+z^2
rearrange and you end up with:
z=sqrt(x^2-y^2)

So:

Grade = (y/sqrt(x^2-y^2))*100

Or you could just use:

Grade=y/x*100

and be very very close.

WOW!

For all intents and purposes, using the distance actually travelled instead of the horizontal distance come out the same. For instance, a 10% grade (5280' horizontal, 528' vertical) has an actual distance travelled (the hypotenuse) of 5306'. Using that value gives a grade of 9.95%. So, the easily-measured actual distance traveled is a more than adequate substitute for the difficult-to-determine horizontal distance.

it's close if you ride wussy grades... ;)

So right you are. 20% comes out to 19.6%. 50% comes out to 44.6%. You ride up stairwells or something?

I thought the formula was:

y/z*100 + 2 (up to 1 year after you rode it)

y/z*100 + 3 (from 1-3 years after you rode it)

y/z*100 + 5 (thereafter)

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kangaroo -- please do not read or respond to any of my posts