How to calculate roof pitch
Roof pitch is the vertical rise for every 12 inches of horizontal run. A 6/12 roof rises 6 inches per foot.
Angle = arctan(rise ÷ run)
Slope % = rise ÷ run × 100
Multiplier = √(1 + (rise ÷ run)²)
Multiply a roof's flat footprint by the multiplier to get its true surface area. The roofing squares calculator does that for you.
Roof pitch in degrees: chart
| Pitch | Degrees | Multiplier | Pitch | Degrees | Multiplier |
|---|---|---|---|---|---|
| 2/12 | 9.46° | 1.014 | 8/12 | 33.69° | 1.202 |
| 3/12 | 14.04° | 1.031 | 9/12 | 36.87° | 1.250 |
| 4/12 | 18.43° | 1.054 | 10/12 | 39.81° | 1.302 |
| 5/12 | 22.62° | 1.083 | 12/12 | 45.00° | 1.414 |
| 6/12 | 26.57° | 1.118 | 14/12 | 49.40° | 1.537 |
| 7/12 | 30.26° | 1.158 | 18/12 | 56.31° | 1.803 |
Three ways to measure roof pitch
1. From the attic (safest)
Hold a 2 ft level against the underside of a rafter with the level horizontal. Make a mark on the level 12 inches from where it touches the rafter, then measure straight up from that mark to the bottom of the rafter. That number is the rise, and the pitch is rise/12.
2. From the gable end
From the ground or a ladder, measure the height of the gable from the top of the wall to the peak (total rise), and half the width of the house at that wall (total run). Enter both in inches. For example, a 24 ft wide house with a peak 6 ft above the wall plate is a total rise of 72 in over a run of 144 in: a 6/12 pitch.
3. With a phone or angle finder
Lay a phone with a level app, or an angle finder, on the roof surface or a rafter and read the angle. Enter it in the angle box. A reading of 30° is a 6.9/12 pitch, which roofers call a 7/12.
What your pitch means for roofing
| Pitch | What it means |
|---|---|
| Below 2/12 | Low slope. Asphalt shingles are not allowed by the residential building code; a membrane roof is used instead. |
| 2/12 to under 4/12 | Shingles are allowed, but the code requires a double layer of underlayment. |
| 4/12 to 9/12 | The normal range for most houses. Standard shingle installation. |
| Above 9/12 | Steep. Expect fall protection and steep-slope labor rates in quotes. |
Once you know the pitch, the roof square footage calculator turns your house footprint into true roof area, and the rafter length calculator gives rafter lengths.
What is a 6/12, 8/12 or 12/12 roof pitch?
A 6/12 roof rises 6 inches for every 12 inches of run, an angle of 26.57°. An 8/12 pitch is 33.69°, and a 12/12 pitch is 45°, a roof that rises as much as it runs. Pitches above about 9/12 are steep roofs that need fall protection and usually cost more to install.
Frequently asked questions
What is the most common roof pitch?
Between 4/12 and 9/12 for most houses in North America, with 6/12 the most common.
What is the minimum pitch for asphalt shingles?
2/12, with double underlayment between 2/12 and 4/12 per most shingle manufacturers and the IRC.
How many degrees is a 4/12 pitch?
18.43 degrees.
Is pitch the same as slope?
People use both terms loosely. Strictly, slope is rise over run (6/12), while pitch is rise over span, but roofers almost always mean rise over a 12-inch run.