Roof Pitch Calculator: Angles, Slopes & Ratios

Roof pitch is a critical measurement in construction and roofing that expresses the steepness of a roof. It's typically represented as a ratio of vertical rise to horizontal run, usually with the run standardized to 12 inches.

Common Roof Pitch Formats

• Pitch Ratio: Expressed as X:12 or X/12 (e.g., 6:12), indicating X inches of rise per 12 inches of horizontal run.
• Angle in Degrees: The angle of the roof slope measured from horizontal (e.g., 26.6°).
• Slope Decimal: Rise divided by run expressed as a decimal (e.g., 0.5).
• Percent Grade: The rise divided by run multiplied by 100 (e.g., 50%).

Roof Pitch Conversion Formulas

• Angle to Slope: Slope = tan(angle)
• Slope to Angle: Angle = arctan(slope) in degrees
• Ratio to Slope: Slope = rise/run
• Slope to Percent: Percent = slope × 100

Why Roof Pitch Matters

The pitch of a roof affects many aspects of construction and performance:

• Water Drainage: Steeper pitches shed water more efficiently, reducing the risk of leaks.
• Material Selection: Different roofing materials require specific minimum pitches to function properly.
• Attic Space: Steeper pitches create more usable space in the attic.
• Snow Load: In snowy regions, pitch affects how snow accumulates and slides off the roof.
• Aesthetics: Pitch significantly impacts the overall look and style of a building.
• Wind Resistance: Different pitches perform differently in high-wind conditions.

Common Roof Pitches by Style

• Flat Roof: 1:12 or less (almost flat, with minimal slope for drainage)
• Low-Slope Roof: 2:12 to 4:12 (commonly used in modern and commercial buildings)
• Conventional Roof: 4:12 to 9:12 (standard for most residential buildings)
• Steep Roof: 9:12 or greater (common in Tudor, Victorian, and Gothic styles)

Understanding roof pitch is essential for proper roofing material selection, accurate material quantity calculations, and ensuring your roof meets local building codes and performs as expected in your climate.