Roof Slope Calculator – Pitch, Angle & Percentage
Calculate roof slope, pitch, and angle from measurements
Table of Contents
How to Use
- Enter the rise (vertical height) of your roof
- Enter the run (horizontal distance) of your roof
- Select your preferred units for each measurement
- Click calculate to see slope ratio, degrees, and percentage
What is Roof Slope?
Roof slope, also known as roof pitch, is the measure of how steep a roof is. It's expressed as the ratio of vertical rise to horizontal run, typically shown as X:12 in roofing.
Understanding roof slope is essential for material selection, water drainage, structural design, and calculating the total roof area for material estimates.
Common Roof Slope Categories
| Category | Pitch Range | Angle | Characteristics |
|---|---|---|---|
| Flat | 0:12 to 2:12 | 0° to 9.5° | Requires special waterproofing |
| Low Slope | 2:12 to 4:12 | 9.5° to 18.5° | Common for modern homes |
| Conventional | 4:12 to 9:12 | 18.5° to 37° | Most common residential |
| Steep | 9:12 to 21:12 | 37° to 60° | Better drainage, more materials |
Why Roof Slope Matters
Roof slope affects several critical aspects of your roofing project:
- Water drainage: Steeper slopes shed water more effectively
- Snow load: Slope helps snow slide off, reducing weight stress
- Material selection: Some materials require minimum slope ratings
- Installation cost: Steeper roofs are more difficult and expensive to work on
- Aesthetics: Slope contributes significantly to building appearance
- Ventilation: Slope affects attic space and ventilation options
Tips for Measuring Roof Slope
- Use a level and tape measure for accurate measurements
- Measure from the bottom edge (eave) to the peak (ridge)
- For safety, measure from inside the attic when possible
- The standard rise is measured over 12 inches of horizontal run
- Consider hiring a professional for steep or complex roofs
- Account for any roof sag or settling in older structures
Frequently Asked Questions
- What is a typical roof slope for residential homes?
- Most residential homes have roof slopes between 4:12 and 9:12 (18.5° to 37°). A 6:12 pitch is very common, providing good drainage while remaining relatively easy to work on.
- How do I measure rise and run?
- Rise is the vertical distance from the roof edge to the peak. Run is the horizontal distance from the same point. For roofing, run is typically measured as 12 inches, and rise is measured over that distance.
- Can I walk on a steep roof safely?
- Roofs steeper than 6:12 become increasingly difficult and dangerous to walk on. Always use proper safety equipment and consider hiring professionals for steep roofs.
- Does roof slope affect material choice?
- Yes, different roofing materials have minimum slope requirements. For example, asphalt shingles typically require at least 2:12, while metal roofing can work on slopes as low as 1:12.
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