1 percent: the least a patio should have
A 1% slope is 0.57°, too little to see by eye. It falls 0.12 inches per foot, close to the 1/8 inch per foot (1.04%) that is about the least a patio needs to drain, and the gentle end of the 1/8 to 1/4 inch per foot a drain pipe needs.
Over 10 feet that is 1.2 inches of fall, so it has to be set with a string line and a line level or a laser. Puddles form wherever the surface dips by more than that.
Across a 12 foot patio the whole fall is 1.44 inches, and a 30 foot run of drain pipe laid at 1% drops 3.6 inches from end to end.
1% slope: rise over a distance
A 1% slope rises 1 feet in every 100 feet of level distance.
| Run (level distance) | Rise in inches | Rise in feet | Length along the slope |
|---|---|---|---|
| 1 ft | 0.12 in | 0.01 ft | 1.00 ft |
| 10 ft | 1.2 in | 0.1 ft | 10.00 ft |
| 20 ft | 2.4 in | 0.2 ft | 20.00 ft |
| 50 ft | 6 in | 0.5 ft | 50.00 ft |
| 100 ft | 12 in | 1 ft | 100.00 ft |
Worked example
1 ÷ 100 = 0.01. The angle is the arctangent of that: arctan(0.01) = 0.57°. As a ratio, 100 ÷ 1 = 100, so the slope is 1 in 100. Per foot, 0.01 × 12 = 0.12 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 |
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 1 percent slope in degrees?
0.57 degrees. Divide the percent by 100 and take the arctangent: arctan(0.01) = 0.57°.
Is a 1 percent slope enough for drainage?
Only just. About 1/8 inch per foot (1.04%) is the least a patio needs, and the common rule next to a house is 1/4 inch per foot (2.08%), twice as much.
How much does a 1% slope rise per foot?
0.12 inches for every foot of run, which is 1.2 inches over 10 feet and 1 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.