PITCH & SLOPE TOOL
Roof Pitch Calculator
Determine exact roof pitch, angle in degrees, slope percentage, and pitch multiplier from your rise and run measurements.
Pitch Diagram & Key Facts
- Pitch Ratio: Expressed as Rise / 12 in North America.
- Pitch Multiplier: Used to multiply ground footprint area to find sloped roof surface area.
- Minimum for Shingles: 2/12 (low slope) or 4/12 (conventional).
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How to Use This Calculator
- Enter the vertical Rise in inches. This represents the vertical height change.
- Enter the horizontal Run in inches. Standard North American run is 12 inches.
- Click Calculate Pitch or adjust values to get real-time updates.
- Review your pitch ratio, incline angle in degrees, slope percentage, and pitch multiplier.
Formulas & Trigonometry
Roof pitch calculations rely on standard right-triangle trigonometry:
- Pitch Ratio: (Rise / Run) × 12
- Angle (Degrees): arctan(Rise / Run) × (180 / π)
- Slope Percentage: (Rise / Run) × 100
- Pitch Multiplier: √((Rise / 12)² + 1)
Standard Roof Pitch Chart
Reference table converting common rise over 12" run into angle degrees and multipliers:
| Roof Pitch | Angle (Degrees) | Slope % | Area Multiplier | Roof Category |
|---|---|---|---|---|
| 1 / 12 | 4.76° | 8.33% | 1.0035 | Flat / Low Slope |
| 2 / 12 | 9.46° | 16.67% | 1.0138 | Low Slope |
| 3 / 12 | 14.04° | 25.00% | 1.0308 | Low Slope |
| 4 / 12 | 18.43° | 33.33% | 1.0541 | Conventional Slope |
| 5 / 12 | 22.62° | 41.67% | 1.0833 | Conventional Slope |
| 6 / 12 | 26.57° | 50.00% | 1.1180 | Conventional Slope |
| 7 / 12 | 30.26° | 58.33% | 1.1577 | Conventional Slope |
| 8 / 12 | 33.69° | 66.67% | 1.2019 | Conventional Slope |
| 9 / 12 | 36.87° | 75.00% | 1.2500 | Steep Slope |
| 10 / 12 | 39.81° | 83.33% | 1.3017 | Steep Slope |
| 12 / 12 | 45.00° | 100.00% | 1.4142 | Steep Slope (45°) |
Frequently Asked Questions
A 4/12 roof pitch means the roof rises 4 inches vertically for every 12 inches of horizontal run. It represents an angle of 18.43 degrees and an area multiplier of 1.0541.
The roof pitch multiplier is computed using the formula √((Rise/12)² + 1). Multiply your building ground footprint area by this multiplier to get the exact sloped roof area.