Dial in the right patio fall for drainage. Switch units, compare slope standards instantly here. Get drop, angle, and layout notes for build success.
| Run | Slope | Calculated Drop | Angle | Notes |
|---|---|---|---|---|
| 12 ft | 2.0% | 2.88 in | 1.146° | Typical fall for many finished surfaces. |
| 4 m | 15 mm/m | 60 mm | 0.859° | Low-to-moderate fall for smooth drainage. |
| 18 ft | 0.125 in per ft | 2.25 in | 0.596° | Good when finish is very flat. |
Patio surfaces must shed water away from doors, walls, and planting beds. A controlled pitch limits puddling, reduces algae growth, and protects jointing materials. Even small runs can hold liters of water when the fall is inconsistent. Use the calculator to translate your target fall into a measurable drop. Consistent drainage also reduces freeze–thaw damage by limiting trapped water at edges and low joints.
Many patios perform well around 1–2.5% fall, depending on finish, texture, and local rainfall intensity. Smooth stone often needs more fall than textured pavers because water films can linger. Steeper slopes improve drainage but can feel uncomfortable for seating and can complicate edge detailing. When space is tight, consider adding a channel drain rather than pushing the whole surface steeper.
Install crews and suppliers describe pitch in different ways: percent, ratio, inches per foot, millimeters per meter, or degrees. The calculator converts each representation to the same dimensionless slope. This avoids rounding errors when switching between tape measures, laser levels, and design notes. For example, 2% equals 0.24 in/ft and 20 mm/m, so the same intent stays clear across teams.
Start from a fixed reference point such as the finished floor threshold. Measure the run in the drainage direction, then apply the calculated drop to find the low point. Mark the high and low elevations on stakes or batter boards. Check intermediate points to keep screed rails straight. Reconfirm with a straightedge or string line so the pitch is uniform across joints and corners.
Confirm the fall continues through door lines, joints, and channel drains. Keep weep holes, expansion gaps, and drainage outlets clear. After placing bedding or concrete, recheck levels before final finishing. A quick hose test can reveal flat spots that should be corrected immediately. If you enter patio width, the diagonal note helps verify that water will not track toward a side wall.
Use the horizontal distance in the drainage direction, from the high point to the low point. Measure along the surface plan, not the sloped face, and include any steps in grade only if the surface is continuous.
It can work on very flat, well-finished surfaces, but it is sensitive to construction tolerances. If your finish, joints, or base are uneven, consider a higher fall or add a drain to reduce standing water.
A 1:N ratio means one unit of drop for every N units of run. Smaller N is steeper. For example, 1:50 means 1 unit down over 50 units across.
They are common site-friendly formats in different regions. Showing both helps you communicate with suppliers and crews, and it also lets you sanity-check that percent, ratio, and angle outputs match your intent.
Yes, in most cases. Falling away helps protect thresholds and wall bases from splashback and pooling. Where constraints exist, use drains, waterproof detailing, or local codes to define the safest discharge path.
Use it as a quick check only. The diagonal note assumes a rectangle with straight edges. For irregular shapes, verify key flow paths with spot levels and confirm that every low point drains to an outlet.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.