Roof Pitch Calculator
Converts roof vertical rise and horizontal run into standard American X/12 pitch slope, roof slope angle in degrees, slope gradient percentage, and area multiplication factors.
Formula
Pitch = Rise / (Run / 12); Angle = arctan(Rise ÷ Run) × (180 ÷ π); Multiplier = √(1 + (Pitch ÷ 12)²)
1. Standardized 12-inch Pitch = (Rise ÷ Run) × 12 2. Slope Angle (Degrees) = arctan(Rise ÷ Run) × (180 ÷ π) 3. Slope Grade % = (Rise ÷ Run) × 100 4. Surface Area Multiplier = √(1 + (Pitch ÷ 12)²)
Inputs
- Vertical Rise (Inches)
- Horizontal Run (Inches - Standard is 12")
Worked example
Calculating slope angle and area multiplier for a 6/12 roof pitch.
Outcome: Pitch is 6/12. Slope angle is 26.57 degrees. Grade is 50.0%. Surface area multiplier is 1.118 (a 1,000 sq ft flat ceiling corresponds to 1,118 sq ft of sloped roof decking).
What is the most common residential roof pitch in America?
The most common residential roof pitches range from 4/12 to 8/12. A 6/12 pitch (26.6° angle) is widely considered the sweet spot for rapid water shedding and safe walkability during maintenance.