100 percent: 45 degrees
A 100% slope is 45.00°, not vertical: the rise equals the run, 1 up for every 1 along. It rises 12 inches per foot, a 12/12 roof pitch.
Percent grade has no upper limit. A vertical wall has no run at all, so its grade cannot be written as a percent.
At 100%, 100 feet of run is 141.42 feet along the slope, about 41% more surface than the footprint.
100% slope: rise over a distance
A 100% slope rises 100 feet in every 100 feet of level distance.
| Run (level distance) | Rise in inches | Rise in feet | Length along the slope |
|---|---|---|---|
| 1 ft | 12 in | 1 ft | 1.41 ft |
| 10 ft | 120 in | 10 ft | 14.14 ft |
| 20 ft | 240 in | 20 ft | 28.28 ft |
| 50 ft | 600 in | 50 ft | 70.71 ft |
| 100 ft | 1,200 in | 100 ft | 141.42 ft |
Worked example
100 ÷ 100 = 1. The angle is the arctangent of that: arctan(1) = 45.00°. As a ratio, 100 ÷ 100 = 1, so the slope is 1 in 1. Per foot, 1 × 12 = 12 inches.
Nearby grades in degrees
| Grade | Angle | Ratio | Rise per foot |
|---|---|---|---|
| 30% | 16.70° | 1 in 3.33 | 3.6 in |
| 33% | 18.26° | 1 in 3.03 | 3.96 in |
| 50% | 26.57° | 1 in 2 | 6 in |
| 100% | 45.00° | 1 in 1 | 12 in |
For any other rise, run or grade use the slope and grade calculator. The guide slope and grade for drainage and ramps covers how much fall each job needs.
Want to change anything else? The calculator above is the full Slope and Grade Calculator: edit any number and the results update instantly.
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Frequently asked questions
What is a 100 percent slope in degrees?
45.00 degrees. Divide the percent by 100 and take the arctangent: arctan(1) = 45.00°.
Is a 100 percent slope vertical?
No. It is 45.00°: 1 foot of rise for every foot of run. Vertical is 90°, which has no percent grade.
How much does a 100% slope rise per foot?
12 inches for every foot of run, which is 120 inches over 10 feet and 100 feet over 100 feet.
Related sizes and guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.