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Roof Pitch Calculator — Angle, Ratio & Slope Grade
Convert rise and run into pitch ratio (X:12), angle in degrees, and percent slope.
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CONSTRUCTION & CODE
More in Roofing & Incline:
Project Specifications
Pitch & Incline Formulas
Transparent mathematical methodology explained in plain English.
Angle (deg) = arctan(Rise / Run) × (180 / π) | Pitch Multiplier = √(1 + (Rise / Run)²) Roof pitch is traditionally expressed as inches of vertical rise per 12 inches of horizontal run.
Variables Explained:
- Standard Run: Base measurement fixed at 12 inches.
Real Project Example
Roof with 7 Inches Rise over 12 Inches Run
Finding the angle and rafter factor of a 7:12 roof.
Sample Project Inputs:
Rise: 7 inches
Run: 12 inches
Step-by-Step Calculation:
- Pitch Ratio: 7:12.
- Slope Decimal: 7 ÷ 12 = 0.5833 (58.3% slope).
- Angle: arctan(0.5833) = 30.26°.
- Rafter Factor: √(1 + 0.5833²) = 1.1577.
Calculated Answer: 7:12 pitch = 30.26° angle with a 1.158 length multiplier.
Knowledge Base
Frequently Asked Questions: Roof Pitch Calculator
Click any question below to expand quick answers, formulas, and expert tips.
What is the minimum roof pitch for asphalt shingles?
Standard asphalt shingles require a minimum 4:12 pitch. They can be installed down to a 2:12 pitch only if double-layer underlayment or full ice and water shield is applied.