Roof Slope & Pitch Calculator
Calculate pitch ratio, degrees, and percentage slope
Results
Understanding Roof Slope and Pitch
Calculating roof slope is a critical step in any construction or roofing project. It determines the type of materials you can use, the drainage efficiency, and the overall structural requirements of the building. While the terms "slope" and "pitch" are often used interchangeably, they represent different ways of describing the roof's steepness.
How to Calculate Roof Slope Manually
To calculate roof slope, you need two primary measurements: the Rise and the Run.
- Rise: The vertical height of the roof.
- Run: The horizontal distance from the edge of the roof to the peak (or a specific horizontal section).
In the United States, roof pitch is typically expressed as a ratio of the rise over a 12-inch run. For example, a "4 in 12" pitch means the roof rises 4 inches for every 12 inches of horizontal run.
The Mathematical Formulas
The calculator above uses the following trigonometric and algebraic formulas to provide accurate results:
- Slope Ratio: Rise / Run
- Pitch (x:12): (Rise ÷ Run) × 12
- Angle in Degrees: arctan(Rise ÷ Run) × (180 ÷ π)
- Slope Percentage: (Rise ÷ Run) × 100
Common Roof Pitch Examples
| Pitch (in 12) | Angle (Degrees) | Typical Use |
|---|---|---|
| Low (2/12) | 9.46° | Sheds, industrial buildings |
| Medium (6/12) | 26.57° | Standard residential homes |
| Steep (12/12) | 45.00° | A-frames, Victorian styles |
Why Slope Matters for Materials
Different roofing materials require specific minimum slopes to prevent leaks:
- Asphalt Shingles: Usually require a minimum of 2/12 pitch (with special underlayment) or 4/12 (standard).
- Clay/Concrete Tiles: Best for 4/12 pitch and above.
- Metal Roofing: Can often be installed on very low slopes (as low as 1/2 in 12 for standing seam).
- Wood Shakes: Generally require a 4/12 pitch or steeper.