25 percent: a 3/12 roof pitch
25% is 14.04°, 1 in 4. It rises 3 inches per foot, which is the same thing as a 3/12 roof pitch: roof pitch and percent grade are the same idea in different units.
On the ground a 1 in 4 bank rises 25 feet over 100 feet of run and measures 103.08 feet along its face.
A roof at this pitch over a 14 foot run rises 3.5 feet from the eave to the ridge.
25% slope: rise over a distance
A 25% slope rises 25 feet in every 100 feet of level distance.
| Run (level distance) | Rise in inches | Rise in feet | Length along the slope |
|---|---|---|---|
| 1 ft | 3 in | 0.25 ft | 1.03 ft |
| 10 ft | 30 in | 2.5 ft | 10.31 ft |
| 20 ft | 60 in | 5 ft | 20.62 ft |
| 50 ft | 150 in | 12.5 ft | 51.54 ft |
| 100 ft | 300 in | 25 ft | 103.08 ft |
Worked example
25 ÷ 100 = 0.25. The angle is the arctangent of that: arctan(0.25) = 14.04°. As a ratio, 100 ÷ 25 = 4, so the slope is 1 in 4. Per foot, 0.25 × 12 = 3 inches.
Nearby grades in degrees
| Grade | Angle | Ratio | Rise per foot |
|---|---|---|---|
| 12% | 6.84° | 1 in 8.33 | 1.44 in |
| 15% | 8.53° | 1 in 6.67 | 1.8 in |
| 20% | 11.31° | 1 in 5 | 2.4 in |
| 25% | 14.04° | 1 in 4 | 3 in |
| 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 |
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 25 percent slope in degrees?
14.04 degrees. Divide the percent by 100 and take the arctangent: arctan(0.25) = 14.04°.
What roof pitch is a 25 percent slope?
3/12: 3 inches of rise for every 12 inches of run, an angle of 14.04°.
How much does a 25% slope rise per foot?
3 inches for every foot of run, which is 30 inches over 10 feet and 25 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.