Roof Pitch Calculator
Calculate roof pitch, slope angle, slope percentage and roof-area multiplier from rise and run measurements.
Your project details
Change the inputs below to match your project.
How the roof pitch calculator works
Roof pitch describes vertical rise compared with horizontal run. A 6:12 roof rises 6 inches for every 12 inches of horizontal run. The calculator uses rise and run to return four planning values: pitch ratio, slope angle, slope percentage and an area multiplier.
Formulas used
| Result | Formula |
|---|---|
| Pitch ratio | Rise : Run |
| Slope percentage | (Rise ÷ Run) × 100 |
| Slope angle | arctangent(Rise ÷ Run) |
| Area multiplier | √(Rise² + Run²) ÷ Run |
Worked example: 6:12 pitch
For a rise of 6 inches and run of 12 inches, slope percentage is 50%, slope angle is about 26.6°, and the area multiplier is about 1.118. A simple 1,000 sq ft horizontal roof footprint would therefore correspond to roughly 1,118 sq ft of sloped surface before overhangs, dormers or other geometry are added.
Common pitch reference
| Pitch | Approx. angle | Area multiplier |
|---|---|---|
| 3:12 | 14.0° | 1.031 |
| 4:12 | 18.4° | 1.054 |
| 6:12 | 26.6° | 1.118 |
| 8:12 | 33.7° | 1.202 |
| 10:12 | 39.8° | 1.302 |
| 12:12 | 45.0° | 1.414 |
What the area multiplier can and cannot do
The multiplier is useful for simple roof planes when you know the horizontal footprint. It does not automatically account for overhangs, valleys, hips, dormers, porch roofs, attached garages or irregular geometry.
Measurement safety
Do not climb onto a roof only to obtain pitch. Whenever possible, use plans, an attic measurement, a professional roof report or a safe ground-based method. Steep and wet roofs present serious fall hazards.
Use pitch in the rest of your planning
After calculating pitch, use the Roofing Square Calculator to convert surface area into squares, then use the Roof Replacement Cost Calculator for a broader budget.
FAQ
Is roof pitch the same as roof angle?
No. Pitch is usually expressed as rise over run, while angle is measured in degrees. They describe the same slope in different ways.
Can I use pitch to estimate exact roof area?
Only for simple geometry. Real roofs often need separate measurements for each plane and overhang.
Why does pitch affect cost?
Pitch can change roof surface area, access, safety requirements and labor difficulty. The actual price impact varies by contractor and project.