Roof Pitch Chart
Every pitch from 1/12 to 24/12, with the angle, the multiplier you have to apply to a footprint, and the rafter length that goes with it.
Pitch is written as inches of rise over 12 inches of run, and almost everything else about a roof falls out of that one fraction. The angle is the arctangent of it. The multiplier is the hypotenuse of the same triangle, which is the number your footprint has to be multiplied by before it means anything. The rafter length is that multiplier again, measured out over whatever run you have.
The table below is the whole relationship in one place. It is the reason a 1,200 square foot footprint is never 1,200 square feet of shingles.
Pitch, angle, multiplier and rafter length
| Pitch | Angle, degrees | Slope multiplier | Grade | Rafter per 12 ft of run |
|---|---|---|---|---|
| 1/12 | 4.8 | 1 | 8.3% | 12.04 |
| 2/12 | 9.5 | 1.01 | 16.7% | 12.17 |
| 3/12 | 14 | 1.03 | 25% | 12.37 |
| 4/12 | 18.4 | 1.05 | 33.3% | 12.65 |
| 5/12 | 22.6 | 1.08 | 41.7% | 13 |
| 6/12 | 26.6 | 1.12 | 50% | 13.42 |
| 7/12 | 30.3 | 1.16 | 58.3% | 13.89 |
| 8/12 | 33.7 | 1.2 | 66.7% | 14.42 |
| 9/12 | 36.9 | 1.25 | 75% | 15 |
| 10/12 | 39.8 | 1.3 | 83.3% | 15.62 |
| 11/12 | 42.5 | 1.36 | 91.7% | 16.28 |
| 12/12 | 45 | 1.41 | 100% | 16.97 |
| 13/12 | 47.3 | 1.47 | 108.3% | 17.69 |
| 14/12 | 49.4 | 1.54 | 116.7% | 18.44 |
| 15/12 | 51.3 | 1.6 | 125% | 19.21 |
| 16/12 | 53.1 | 1.67 | 133.3% | 20 |
| 17/12 | 54.8 | 1.73 | 141.7% | 20.81 |
| 18/12 | 56.3 | 1.8 | 150% | 21.63 |
| 19/12 | 57.7 | 1.87 | 158.3% | 22.47 |
| 20/12 | 59 | 1.94 | 166.7% | 23.32 |
| 21/12 | 60.3 | 2.02 | 175% | 24.19 |
| 22/12 | 61.4 | 2.09 | 183.3% | 25.06 |
| 23/12 | 62.4 | 2.16 | 191.7% | 25.94 |
| 24/12 | 63.4 | 2.24 | 200% | 26.83 |
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The roof pitch calculator takes your own measurements and returns the number for your job, plus the material list as a printable document. Every cell in the table above came out of that same calculator, run at build time.
How to read the multiplier column
The multiplier converts flat area into roof area. A 6/12 roof is 1.12 times its own footprint, so 1,200 square feet of ground under it is about 1,342 square feet of roof surface. At 12/12 the same footprint is 1.41 times, which is over 400 extra square feet of shingles on a house that measures identically from above.
This is the single most commonly skipped step in a roofing takeoff, and it always skips in the same direction: short. Nobody has ever accidentally ordered too much by forgetting it.
Measuring pitch without getting on the roof
Hold a level out from a rafter, gable end or fascia, mark 12 inches along it, and measure straight down from that mark to the roof line. That measurement in inches is the rise, and the pitch is that over 12. From inside an attic you can do the same thing against the underside of a rafter.
If the number lands between two pitches, take the lower one for angle work and the higher one for material. You would rather have an extra bundle than be a bundle short on a Saturday.
Where pitch stops being a preference
Below about 2/12 most asphalt shingle manufacturers will not warrant the roof at all, and between 2/12 and 4/12 they require a double layer of underlayment or a full self adhering membrane. Above about 8/12 the job needs roof jacks and staging, which is a labor number rather than a material one.
Check the installation instructions for the shingle actually going on the roof. The low slope limits are a manufacturer rule and a code rule, not a rule of thumb, and they are the rule that voids a warranty fastest.
Questions people ask
What is the most common roof pitch on a house?
In American residential construction most roofs land between 4/12 and 9/12. Anything under 4/12 is usually a porch, an addition or a low slope commercial roof, and anything over 12/12 is usually a steep architectural gable or a roof built where snow load drove the design.
What angle is a 6/12 pitch?
26.6 degrees. It is also a 50 percent grade, and its slope multiplier is 1.12, so a 6/12 roof has 12 percent more surface than the ground it covers.
Is a 12/12 roof really 45 degrees?
Yes. Twelve inches of rise over twelve inches of run is a square corner cut in half, so the angle is exactly 45 degrees, the grade is exactly 100 percent, and the multiplier is the square root of 2.
What is the difference between pitch, slope and grade?
On an American job site pitch and slope are used interchangeably and both mean rise over 12 inches of run. Grade is the same ratio written as a percent, which is how a civil drawing or an excavation plan states it.