Road Cycling - How do you calculate the gradient of a hill?

I was trying to figure out what % the hill I climb for training is... Dunno if I am doing it right...

Its 7/10 of a mile, and there is an elevation gain of 345ft. The number I came up with was around 10.5% but that seems awfully high... (but then again, it is pretty steep...)

I will usually climb it twice in my normal 20 mile loop...

Grade = vertical gain / horizontal distance

Your horizontal distance of .7 mile = 3696 ft

345 ft of gain / 3696 ft = .09334... or approximately 9/100ths which is a 9% grade.

Grade = vertical gain / horizontal distance

Your horizontal distance of .7 mile = 3696 ft

345 ft of gain / 3696 ft = .09334... or approximately 9/100ths which is a 9% grade.

That is my understanding of how it is calculated. By the way, a 9% grade is respectably steep and not that common. I believe state routes have to be 7% or less and generally interstate highways are even less.

Skip the math. Different points of a climb may be steeper than others. The inclinometer isn't exactly high tech but is accurate enough.
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I have an inclinometer..Keeps getting bumped. Do you need a level to set it..

I have an inclinometer..Keeps getting bumped. Do you need a level to set it..

I put mine close to the stem and I don't have any trouble with bumping it. As for leveling I just find level
ground and move the inclinometer until the bubbles centered.

Isnt there some computers that have that fuction?

Isnt there some computers that have that fuction?

Probably, but since I already have an altimeter, I figured I could figure it out fairly easy without having to replace my computer. :)

More accurate would be to say:

%grade=vertical gain or loss/**distance traveled** (true "horizontal distance" will always be less than the distance traveled if the the grade is not zero)

More accurate would be to say:

%grade=vertical gain or loss/**distance traveled** (true "horizontal distance" will always be less than the distance traveled if the the grade is not zero)

An excellent point. A local hill (1.8 miles) calculates to 12.5% grade using the aformentioned rise over run method, but if you trace out the route in TOPO software, TOPO says it is a 16% grade because it uses the mathematically correct formula for slope.

Isnt there some computers that have that fuction?

Yes, there are several...

I have used a Ciclosport "CicloMaster" CM414Alti for several years. They are not inexpensive but they provide a wealth of information that can also be downloaded to your PC. It records current altitude, altitude gained/lost, total for the day, max achieve as well as current % grade, max grade up/down for the day, average grade up/down. The "real time" display of % grade is not always accurate at a given moment on short climbs or ones where it changes rapidly, e.g., there is a bit of a lag. However, the data that is downloaded to the PC is very accurate and does not reflect the momentary "real time" erroneous data that you sometimes see. The "real time" error stuff is very minor and doesn't detract from the (pick one) usefulness / utility / interest / novelty of the computer.

I have also experimented with a Specialized model that is manufactured by the same company who makes the Ciclosport model. The Specialized model seemed to have less functionality and was more difficult to navigate through, but seemed to have a faster sampling rate.

GPS devices can also be used to ascertain grade.

Note: You will find detractors of barometric-based altimeter devices who cite problems with regard to accuracy. In practice, there is probably 5-10% variability in these devices. We have the CM414alti on the front of our tandem, on the back, we ride with a couple who have a Cateye Altimeter, and another couple that has a Suunto Altimeter. The Avocet Vertech seems to have the highest sampling rate and is the most accurate whereas the CM414 doesn't always collect minor gains or the first few feet of a major gain in altitude. The Cateye and Suunto are a little variable but seem to err on the high side.

How can you deal with these variations? 1. You can recalibrate your altimeter each day to obtain the most accurate data and, notwithstanding the arrival of a weather front during your ride, you WILL have relatively accurate data. 2. You can choose to look only at the "variance" or "delta" data (net gain, etc..) and never recalibrate the device and still have relatively accurate data. 3. You can compare the data you collect with your Altimeter to the data produced by Topo USA Ver. 4 which is absolutely wrong more times than it is right to make you feel better about your Altimeter. 4. You can use a GPS device and get the most accurate data possible.

How do you calculate the gradient of a hill?

Generally, I know if it's more than 10% after a kilometer because:

a) my legs are burning
b) my lungs are about to explode
c) I'm about to pass out and roll into a ditch.

Try riding the four gap in Vermont.It will make you wish you didn't have a inclinometer.I am pretty sure we are talking about 20 + degrees.

How can you deal with these variations? 1. You can recalibrate your altimeter each day to obtain the most accurate data and, notwithstanding the arrival of a weather front during your ride, you WILL have relatively accurate data.

Polar's included software for the S720i has a feature that allows you to set the ending altitude equal to the beginning, which adjusts for weather change at least partly. Since it changes the data for the whole exercise, if the barometric pressure changes only during the second half or very quickly, it'll adjust portions that shouldn't be adjusted, but it's still better than nothing. I've had beginning and ending altitudes recorded as 200-300 feet apart when they're the exact same spot. Adjusting the altitude at least gave me a better idea of the profile than the raw data.