Roof Pitch Calculator – Chart, Multiplier & Angle
Calculate roof pitch, angle, and multiplier factor. Free online roof pitch calculator with chart for common roof slopes.
in
in
sq ft
Common Roof Pitch Factors
| Pitch | Angle | Factor |
|---|---|---|
| 1/12 | 4.76° | 1.003 |
| 2/12 | 9.46° | 1.014 |
| 3/12 | 14.04° | 1.031 |
| 4/12 | 18.43° | 1.054 |
| 5/12 | 22.62° | 1.083 |
| 6/12 | 26.57° | 1.118 |
| 7/12 | 30.26° | 1.158 |
| 8/12 | 33.69° | 1.202 |
| 9/12 | 36.87° | 1.250 |
| 10/12 | 39.81° | 1.302 |
| 11/12 | 42.51° | 1.357 |
| 12/12 | 45.00° | 1.414 |
Roof Pitch Calculator Formula
Pitch Factor = √(Rise² + Run²) / Run
How to Calculate Roof Pitch
- 1. Determine the rise (vertical distance) per 12 inches of run
- 2. Calculate the pitch factor: √(Rise² + Run²) ÷ Run
- 3. Calculate the angle: Angle = arctan(Rise ÷ Run) in degrees
- 4. If you have a base area, multiply by the pitch factor to get actual roof area
Example Calculation
Let's say you're calculating the pitch for a roof with 6 inches of rise per 12 inches of run.
- rise: 6
- run: 12
- baseArea: 1000 sq ft
Pitch ratio is 6/12, angle is 26.57°, pitch factor is 1.118. Actual roof area for 1000 sq ft base = 1,118 sq ft
Tips
- A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal run
- Standard roof pitch is between 4/12 and 9/12 — most residential roofs fall in this range
- Low-slope roofs (below 4/12) may require special waterproofing membranes
- The pitch factor is essential for ordering the correct amount of roofing materials
Frequently Asked Questions
What is a good roof pitch?
A pitch between 4/12 and 9/12 is considered standard for most residential roofs. Pitches above 9/12 are steep roofs, while those below 4/12 are considered low-slope and may need special materials.
What is the most common roof pitch?
The most common residential roof pitch in the US is between 6/12 and 8/12. This range provides good water drainage while remaining walkable for maintenance.
How do you calculate roof pitch from the ground?
Measure 12 inches horizontally (the run) on a level from the roof surface, then measure the vertical distance (rise) at that point. The ratio of rise to 12 inches of run is your pitch.
What does a 6/12 roof pitch mean?
A 6/12 pitch means the roof rises 6 inches vertically for every 12 inches of horizontal distance. This equals an angle of approximately 26.57 degrees and a pitch factor of 1.118.