What roof pitch means
Roof pitch is the steepness of a roof, written as rise over run — how many inches it climbs per 12 inches of horizontal distance. A roof rising 6 inches over a 12-inch run is a 6:12 pitch, equal to about a 26.6° angle. The slope multiplier (1.118 for 6:12) converts the flat footprint area into the actual sloped roof area. Expressed as a percentage the same slope is what the elevation grade calculator reports.
How to use this calculator
Enter the rise and the run in inches (run is usually 12). The result gives the angle in degrees, the standard X:12 pitch ratio, and the slope multiplier. To estimate roofing materials, multiply your building's flat footprint by the slope multiplier to get the true roof area. Pitch increases the surface you have to cover, which the roof shingle calculator accounts for.
Common roof pitches
| Pitch | Angle | Slope × |
|---|---|---|
| 3:12 | 14.0° | 1.031 |
| 4:12 | 18.4° | 1.054 |
| 6:12 | 26.6° | 1.118 |
| 9:12 | 36.9° | 1.250 |
| 12:12 | 45.0° | 1.414 |
Low-slope vs. steep roofs
Pitches under about 3:12 are considered low-slope and need special membrane roofing, not standard shingles. Pitches of 4:12 to 9:12 are typical for shingled homes. Steeper roofs shed water and snow better but use more material — the higher slope multiplier means more square footage to cover. Footprint area is measured first with the square footage calculator.
Frequently asked questions
- How do I calculate roof pitch?
- Divide the rise by the run. A 6-inch rise over a 12-inch run is a 6:12 pitch, which is about 26.6 degrees.
- What is a 6:12 roof pitch in degrees?
- About 26.6 degrees, with a slope multiplier of 1.118.
- What is the slope multiplier for?
- Multiply your roof's flat footprint area by the slope multiplier to get the actual sloped surface area for ordering materials.
- What roof pitch is too low for shingles?
- Generally below 3:12. Low-slope roofs need membrane systems rather than standard asphalt shingles.
- How do I measure roof pitch safely?
- Work inside the attic. Hold a level horizontally against a rafter, mark 12 inches along it, then measure straight down to the rafter. That drop in inches is the rise for a 12-inch run.