Slope Calculator

Convert between slope percentage, angle in degrees, and rise:run ratio for roofs, driveways, drainage, ramps, and grading.

Slope Calculator

Rise

Run

Common References

Slope Diagram

Slope

33.33%

Rise ÷ Run × 100

Angle

18.43°

Degrees from horizontal

Ratio

4:12

Rise per 12 units of run

Rise per Foot

0.333

Units of rise per 1 unit of run

Slope Summary

This slope rises 4.00 units for every 12 units of horizontal run (4:12), which is a 33.33% grade at 18.43° from horizontal.

Steep slopeSlopes above 25% are considered steep for driveways and walkways. Check local codes — many jurisdictions limit driveway slopes to 15–25%. Stairs or switchback paths may be required for pedestrian access.

This calculator provides geometric slope conversions for reference. Always verify slopes with a level and measuring tools on site. Consult local building codes for minimum and maximum grade requirements.