I am trying to go from layout level to 12 inches below the level. I would like to have a 2 degree slope for this run. Can anyone tell me how long the the slope would have to be to get to 12 inches.

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Original Post

sin 2= 12/x

Solve for X (its about 352" or 29 feet and change).

Typically though, grades are measured in percentages as rise over run, so a 2% grade would be 12/0.02...600" or 50 feet.

There are calculators online.

50 feet.    Simply divide the height you want to reach by the % grade as a fraction 2%  = 2/100 = .02.    So 12 divided by .02  = 600 inches which is 50 feet  (600 inches/12 inches per foot).

You may need a few extra feet on either end for an easement / transition grade.

sin 2= 12/x

Solve for X (its about 352" or 29 feet and change).

Typically though, grades are measured in percentages as rise over run, so a 2% grade would be 12/0.02...600" or 50 feet.

There are calculators online.

Remember 2 deg != 2%

As others mentioned here, percentage of slope is what is typically used and not degrees. It is much easier to think in terms of inches instead of degrees or radians. A 2.5% grade is 2 1/2" over a 100" run. A 2% grade is 2" over 100" run. Now 100" is really close to 8 feet so you can guess-timate about 8 feet for each 2" rise. You want 12" at 2% you need 48 feet. A 12" rise at 2.5% requires about 38 1/2 feet. At 3" the run you need is down to 32 feet.

That's all well and good but there is no consideration for vertical easements on both ends. What I've come to understand is the length and number of transitions are functions of the length of the longest engine and what the final grade is at the end of the transition. For 2, 2 1/2" slope and with a engine length of about 20" I try to transition 2 times, every 30-40 inches. The first transition is about .6%, then about 1.3% and finally reach the 2.5% grade over a total of 6 or 7 feet. This is at both ends.

You can plug in what numbers you want but usually the run distance is restricted by physical limitations so you start compromising. You can use a steeper slopes and reduce the run distance but you may need more transitions to get to that grade, so you gain here and lose there, etc. and hopefully iterate to workable solution.

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