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Roof Pitch Calculator
Convert a measured rise and run into the standard rise:12 pitch notation roofers use.
Roof pitch in rise:12 notation, with the angle and area multiplier for each
Every row is one inch of rise per 12 inches of run. The angle is the calculator output for that rise over a 12 inch run, rounded to one decimal. The slope factor is what you multiply a building footprint by to get the actual sloped roof area, useful when sizing shingles.
| Pitch (rise:12) | Angle (degrees) | Slope factor (footprint to roof area) | What it is used for |
|---|---|---|---|
| 1:12 | 4.8 | 1.003 | Low slope, needs membrane roofing |
| 2:12 | 9.5 | 1.014 | Minimum for most shingles, with extra underlayment |
| 3:12 | 14.0 | 1.031 | Shallow shingle roof, easy to walk |
| 4:12 | 18.4 | 1.054 | Common on ranch and porch roofs |
| 5:12 | 22.6 | 1.083 | Common residential pitch |
| 6:12 | 26.6 | 1.118 | The most common residential pitch |
| 7:12 | 30.3 | 1.158 | Walkable with care |
| 8:12 | 33.7 | 1.202 | Steep, roof jacks or staging needed |
| 9:12 | 36.9 | 1.250 | Not walkable, fall protection required |
| 10:12 | 39.8 | 1.302 | Steep, common on Tudor and gothic styles |
| 12:12 | 45.0 | 1.414 | A 45 degree roof, scaffolding territory |
Pitch is always written as rise per 12 inches of run regardless of the run you measured, and the calculator normalizes any rise and run pair to that form. Anything under 2:12 is low slope and needs a membrane or built-up system rather than shingles, because shingles rely on gravity to shed water. The slope factor is the square root of 1 plus the pitch squared, which is not one of the calculator outputs but is the number that turns a footprint into the roof area the shingle calculator expects. Working above about 7:12 without proper fall protection is dangerous, and many jurisdictions require it.
Why pitch is expressed as X:12
Roofing pitch is conventionally expressed as inches of rise per 12 inches of horizontal run (like '6:12'), regardless of the actual run measured — this calculator normalizes any rise/run measurement to that standard notation.
Pitch affects material choice
Low-slope roofs (under about 2:12) generally need membrane roofing rather than standard shingles, since shingles rely on steep enough pitch to shed water quickly — very steep roofs (over 9:12) need special safety consideration during installation.
Frequently asked questions
My roof rises 6 inches over a 12-inch horizontal run — what pitch is that?
6:12 pitch, which equals about 26.6 degrees. That's a common residential pitch — steep enough for standard shingles, walkable with caution, and sheds water well.
What roof pitch is considered 'flat'?
Anything under 2:12 (about 9.5 degrees) is considered low-slope or 'flat.' These roofs need membrane or built-up roofing rather than standard shingles, because shingles can't shed water reliably at such low angles.
How do I measure my roof pitch from inside the attic?
Hold a level horizontally against a rafter, measure 12 inches along the level from where it touches the rafter, then measure the vertical distance from the end of the level down to the rafter. That vertical measurement is your rise per 12 inches of run.
How does roof pitch relate to the shingle calculator?
Pitch affects actual roof area — a steeper pitch means more surface area than the building's footprint suggests. Calculate your pitch here, then use the pitch multiplier to convert footprint area to actual roof area for the shingle calculator.
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Last updated: September 6, 2026