International Residential Code (IRC Chapter 9)
Roof Pitch Chart: Degrees, Slope Multipliers & Materials
Roof pitch indicates the number of vertical inches a roof rises for every 12 inches of horizontal run. Use this engineering chart to calculate rafter lengths, surface area factors, and IRC roofing code compliance.
| Pitch (Rise : Run) | Angle in Degrees | Area Slope Factor | Slope Classification | Recommended Covering Materials |
|---|---|---|---|---|
| 1:12 | 4.76° | 1.0035 | Low Slope / Flat | EPDM Rubber, TPO, Built-Up Roofing (BUR) |
| 2:12 | 9.46° | 1.0138 | Low Slope | Self-adhering roll roofing, standing seam metal |
| 3:12 | 14.04° | 1.0308 | Low / Conventional | Asphalt shingles (double underlayment required), metal panels |
| 4:12 | 18.43° | 1.0541 | Standard Conventional | Architectural asphalt shingles, standing seam metal |
| 5:12 | 22.62° | 1.0833 | Standard Conventional | Asphalt shingles, clay tiles, cedar shakes |
| 6:12 | 26.57° | 1.1180 | Standard Conventional | Asphalt shingles, slate, concrete tiles, metal |
| 7:12 | 30.26° | 1.1577 | Standard / Steep | Asphalt shingles, synthetic slate, standing seam |
| 8:12 | 33.69° | 1.2019 | Steep Slope | Asphalt shingles, cedar shake, slate, architectural tiles |
| 9:12 | 36.87° | 1.2500 | Steep Slope | All steep slope materials; safety harness required |
| 10:12 | 39.81° | 1.3017 | Steep Slope | Slate, high-end shingles, Victorian / Gothic designs |
| 12:12 | 45.00° | 1.4142 | Very Steep | A-frame, Gothic Revival, steep architectural gables |
| 14:12 | 49.40° | 1.5370 | Mansard / Chalet | Hand-nailed steep shingles, standing seam metal |
| 18:12 | 56.31° | 1.8028 | Extreme / Mansard | Vertical standing seam, ornamental slate shingles |
Rafter Slope Multiplier Formula
Multiply flat building footprint area by the slope multiplier to calculate true pitched surface area:
Multiplier = √((Rise² + 12²) / 12²)
Cite This Engineering Chart
Standard Citation (APA Format):
Calculator Engineering Group. (2025). Roof Pitch Chart: Degrees, Slope Multipliers & Materials. Calculator Construction Reference Tables. https://celculator.com/reference/roof-pitch-chart
Calculate True Shingle Squares & Pitch Factors
Enter building length, width, overhangs, and pitch ratio to calculate bundles of asphalt shingles, underlayment rolls, and hip/ridge cap shingles.