Roof Pitch Calculator
Calculate roof slope, angle, and pitch ratio (X/12)
Calculation Results:
Understanding Roof Pitch Calculations
Roof pitch is a numerical measurement that represents the steepness of a roof. In the construction industry, particularly in North America, pitch is expressed as a ratio of the vertical "rise" over a horizontal "run" of 12 units (usually inches).
How the Calculation Works
The math behind roof pitch involves basic trigonometry and geometry. To calculate the pitch manually, follow these formulas:
- Pitch Ratio: Calculated as (Rise / Run) × 12. For example, a 6-inch rise over a 12-inch run results in a 6/12 pitch.
- Angle in Degrees: Use the arctan formula:
Angle = arctan(Rise / Run) × (180 / π). - Percentage Grade: Simply
(Rise / Run) × 100. - Slope Factor: Calculated as
√(Rise² + Run²) / Run. This factor helps estimate the actual surface area of the roof based on the flat footprint.
Common Roof Pitch Examples
| Pitch (X/12) | Angle | Description |
|---|---|---|
| 2/12 | 9.46° | Low Slope (requires special roofing) |
| 4/12 | 18.43° | Standard Conventional Slope |
| 6/12 | 26.57° | Moderate Slope |
| 12/12 | 45.00° | Steep Slope (45 degree angle) |
Why Pitch Matters
The pitch of a roof determines which materials can be used. Asphalt shingles are typically suitable for pitches between 4/12 and 12/12. Very flat roofs (below 2/12) usually require membrane systems like EPDM or TPO to prevent water penetration, while extremely steep roofs might require specialized safety equipment and specific installation techniques for slate or tile.