Roof pitch & slope calculator
Short answer
Roof pitch is the rise in inches per 12 inches of run. A 6/12 pitch means the roof rises 6 inches over every 12 inches — a 26.57° angle, a 50% grade, and a slope factor of 1.118 (the roof surface is 11.8% larger than its flat footprint). Enter your rise and run, or an angle, for any pitch.
Pitch is the rise in inches per 12" of horizontal run. Measure the rise over a level 12" span, or enter the angle. The slope factor turns a flat footprint into true sloped roof area.
Pitch
6:12
rise / 12" run
Angle
26.57°
50.0% grade
Slope factor
×1.1180
footprint → roof area
Roof type
Conventional
Conventional walkable pitch — standard shingle territory.
Common roof pitches
| Pitch | Angle | Grade | Slope factor |
|---|---|---|---|
| 1/12 | 4.76° | 8% | ×1.0035 |
| 2/12 | 9.46° | 17% | ×1.0138 |
| 3/12 | 14.04° | 25% | ×1.0308 |
| 4/12 | 18.43° | 33% | ×1.0541 |
| 5/12 | 22.62° | 42% | ×1.0833 |
| 6/12 | 26.57° | 50% | ×1.1180 |
| 7/12 | 30.26° | 58% | ×1.1577 |
| 8/12 | 33.69° | 67% | ×1.2019 |
| 9/12 | 36.87° | 75% | ×1.2500 |
| 10/12 | 39.81° | 83% | ×1.3017 |
| 12/12 | 45.00° | 100% | ×1.4142 |
How to calculate roof pitch
Roof pitch is the number of inches a roof rises for every 12 inches of horizontal run. To measure it, hold a level horizontally against the roofline, mark 12 inches along it, then measure straight down from that mark to the roof — that vertical distance is your rise. A rise of 6 inches over a 12-inch run is a "6/12" pitch.
The pitch drives everything else: the angle (arctan of rise ÷ 12), the grade (rise ÷ run as a percentage), and the slope factor — the multiplier that converts the flat footprint under your roof into the larger, sloped surface you actually shingle. Steeper pitches mean more material, more waste, and more labor.
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Open the roofing calculatorFrequently asked questions
How do I calculate roof pitch?
Measure the vertical rise over a level 12-inch run — the pitch is written as rise/12 (for example 6/12). You can measure in the attic against a rafter with a level and tape, or on the roof surface. If you know the angle instead, switch to "Angle" above and the calculator converts it to pitch, grade, and slope factor.
What angle is a 6/12 roof pitch?
A 6/12 pitch is 26.57° from horizontal — a 50% grade. Its slope factor is 1.118, so the sloped roof area is 11.8% larger than the flat footprint beneath it.
How do I convert roof pitch to degrees?
The angle equals arctangent of rise divided by 12: angle = atan(rise ÷ 12). A 4/12 pitch is 18.43°, 6/12 is 26.57°, 9/12 is 36.87°, and 12/12 is 45°.
What is the roof pitch multiplier (slope factor)?
The slope factor is √(rise² + 12²) ÷ 12. Multiply your flat footprint (ground) area by it to get the true sloped roof area you actually have to cover. A 6/12 roof has a factor of 1.118; a 12/12 roof is 1.414.
What is the difference between roof slope and roof pitch?
In everyday roofing they mean the same thing: the rise per 12 inches of run, written as x/12 or as an angle in degrees. Strictly, "slope" is rise over run and "pitch" is rise over the full span, but most calculators, suppliers, and contractors use them interchangeably as x/12.
What roof pitch is walkable?
Up to about 6/12 (26.57°) is comfortably walkable for most people. From 7/12 to 9/12 you should use caution and soft-soled shoes; steeper than 9/12 usually needs roof jacks, staging, or a harness.