Roof Slope Calculator
Calculate slope percentage and angle from roof measurements
in
in
Slope
50.0%
Angle26.6°
Slope Multiplier1.118
Pitch (rise:12)6.00
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How to Use the Roof Slope Calculator
The Roof Slope Calculator converts between the three common ways to express roof slope: pitch ratio (rise:12), angle in degrees, and percentage. Use any measurement you have on hand.
- Select the input format you are starting with: rise & run, degrees, or percentage.
- Enter your known value in the field provided.
- The calculator instantly converts to all other formats.
- Use the pitch multiplier to convert footprint area to actual roof area.
- Check the recommended minimum pitch for your roofing material in the result notes.
Formula & Methodology
The Roof Slope Calculator uses the following established formulas:
Pitch Ratio = rise : 12 (e.g., 6:12)
Degrees = arctan(rise / 12) × (180 / π)
Percentage = (rise / 12) × 100
Multiplier = √(1 + (rise / 12)²)
A 6:12 pitch equals 26.57° and a 50 % slope — all three describe the same roof.
Frequently Asked Questions
Most residential roofs fall between 4:12 and 9:12 (18° – 37°). Low-slope roofs are 2:12 or less, while steep roofs are anything above 9:12. The most common pitch in the US is 6:12.
Asphalt shingles require a minimum 2:12 pitch (with modified installation) and work best at 4:12 and above. Metal roofing can go as low as 1:12 with proper seaming. Always check your material's technical data sheet.
Steeper roofs cost more because they require additional safety equipment, take longer to install, and use more material per square foot of footprint. Expect to add 10–30 % to labor costs for roofs above 7:12.