2 percent: the standard fall for drainage
2% is 1.15° and 0.24 inches per foot, almost exactly the 1/4 inch per foot (2.08%) that is the common rule for water to drain away from a house or across a patio.
Over the first 10 feet from a foundation it comes to 2.4 inches of fall, and across a 12 foot patio 2.88 inches. It still looks flat, and a table on it sits level enough.
To set it out, stretch a level string from the high side and measure down: 4.8 inches at 20 feet, 12 inches at 50 feet.
2% slope: rise over a distance
A 2% slope rises 2 feet in every 100 feet of level distance.
| Run (level distance) | Rise in inches | Rise in feet | Length along the slope |
|---|---|---|---|
| 1 ft | 0.24 in | 0.02 ft | 1.00 ft |
| 10 ft | 2.4 in | 0.2 ft | 10.00 ft |
| 20 ft | 4.8 in | 0.4 ft | 20.00 ft |
| 50 ft | 12 in | 1 ft | 50.01 ft |
| 100 ft | 24 in | 2 ft | 100.02 ft |
Worked example
2 ÷ 100 = 0.02. The angle is the arctangent of that: arctan(0.02) = 1.15°. As a ratio, 100 ÷ 2 = 50, so the slope is 1 in 50. Per foot, 0.02 × 12 = 0.24 inches.
Nearby grades in degrees
| Grade | Angle | Ratio | Rise per foot |
|---|---|---|---|
| 1% | 0.57° | 1 in 100 | 0.12 in |
| 2% | 1.15° | 1 in 50 | 0.24 in |
| 5% | 2.86° | 1 in 20 | 0.6 in |
| 8.33% | 4.76° | 1 in 12 | 1 in |
| 10% | 5.71° | 1 in 10 | 1.2 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.
Tools & materials for this project
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Frequently asked questions
What is a 2 percent slope in degrees?
1.15 degrees. Divide the percent by 100 and take the arctangent: arctan(0.02) = 1.15°.
Is a 2 percent slope the same as 1/4 inch per foot?
Very nearly. 1/4 inch per foot is 2.08%, and 2% is 0.24 inches per foot. Over 10 feet the difference is 0.1 of an inch.
How much does a 2% slope rise per foot?
0.24 inches for every foot of run, which is 2.4 inches over 10 feet and 2 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.