Rise 6 inches over a 12 inch run
I know the Rise and run
Your roof is a 6/12 pitch (26.6 degrees): multiply the footprint by 1.118 for roof area.
- Roof pitch
- 6/12
- Angle
- 26.6
- Pitch factor (roof area multiplier)
- 1.118
- Slope
- 50.0%
- For asphalt shingles
Roof pitch calculator
Your roof pitch from a rise and run or an angle, with the angle, pitch factor and slope.
Your roof
6/12 pitch
6 inches of rise per 12 inches of run 26.6° angle
1.118 pitch factor
50% slope
Add it to build one shopping list for your whole job.
Checked by Junayd
Your roof is a 6/12 pitch (26.6 degrees): multiply the footprint by 1.118 for roof area.
How do you calculate roof pitch?
Roof pitch is the rise in inches over 12 inches of level run. Measure the rise over any level distance, divide by that distance and multiply by 12: a 9 inch rise over 24 inches is 4.5/12. A 6/12 roof rises 6 inches per foot, at 26.6 degrees.
Common roof pitches
| Pitch | Angle | Factor |
|---|---|---|
| 1/12 | 4.8° | 1.003 |
| 2/12 | 9.5° | 1.014 |
| 3/12 | 14.0° | 1.031 |
| 4/12 | 18.4° | 1.054 |
| 5/12 | 22.6° | 1.083 |
| 6/12 | 26.6° | 1.118 |
| 7/12 | 30.3° | 1.158 |
| 8/12 | 33.7° | 1.202 |
| 9/12 | 36.9° | 1.250 |
| 10/12 | 39.8° | 1.302 |
| 11/12 | 42.5° | 1.357 |
| 12/12 | 45.0° | 1.414 |
How we worked it out
- 6 in ÷ 12 in = 0.5
- 0.5 × 12 = 6, so a 6/12 pitch
- Angle: arctan(0.5) = 26.6°
- Pitch factor: √(1 + 0.5²) = 1.118
- Slope: 0.5 × 100 = 50%
The working shows here once your sizes are filled in.
Roof pitch table
| Pitch | Angle (degrees) | Pitch factor | Slope (percent) |
|---|---|---|---|
| 1/12 | 4.8 | 1.003 | 8.3 |
| 2/12 | 9.5 | 1.014 | 16.7 |
| 3/12 | 14.0 | 1.031 | 25.0 |
| 4/12 | 18.4 | 1.054 | 33.3 |
| 5/12 | 22.6 | 1.083 | 41.7 |
| 6/12 | 26.6 | 1.118 | 50.0 |
| 7/12 | 30.3 | 1.158 | 58.3 |
| 8/12 | 33.7 | 1.202 | 66.7 |
| 9/12 | 36.9 | 1.250 | 75.0 |
| 10/12 | 39.8 | 1.302 | 83.3 |
| 11/12 | 42.5 | 1.357 | 91.7 |
| 12/12 | 45.0 | 1.414 | 100.0 |
Worked out at build time by the same maths as the calculator above.
What pitch does each roofing material need?
Each roofing material has a minimum pitch in the International Residential Code. Asphalt shingles need at least 2/12, concrete and clay tile 2.5/12, cedar shake 3/12 and natural slate 4/12. Standing seam metal can go as low as 0.25/12.
Worked examples
Rise 9 inches over a 24 inch level
I know the Rise and run
Your roof is a 4.5/12 pitch (20.6 degrees): multiply the footprint by 1.068 for roof area.
- Roof pitch
- 4.5/12
- Angle
- 20.6
- Pitch factor (roof area multiplier)
- 1.068
- Slope
- 37.5%
- For asphalt shingles
A 45 degree roof
I know the Angle
Your roof is a 12/12 pitch (45.0 degrees): multiply the footprint by 1.414 for roof area.
- Roof pitch
- 12/12
- Angle
- 45.0
- Pitch factor (roof area multiplier)
- 1.414
- Slope
- 100.0%
- For asphalt shingles
Common questions
How do you measure roof pitch?
In the attic, hold a level against a rafter and mark 12 inches along the level. Measure straight up from that mark to the rafter: that height is the rise per 12.
What is a 12/12 pitch roof?
A 12/12 roof rises 12 inches for every 12 inches of run, so it slopes at 45 degrees. Its pitch factor is 1.414: the roof has about 41% more area than its footprint.
What roof pitch is 30 degrees?
A 30 degree roof has a pitch of about 6.9/12, a rise of 6.9 inches per foot of run. The nearest whole pitch is 7/12, at 30.3 degrees.
What is the angle of a 4/12 pitch roof?
A 4/12 roof slopes at 18.4 degrees, with a pitch factor of 1.054. Below 4/12, asphalt shingles need two layers of underlayment.
What is the minimum pitch for asphalt shingles?
Asphalt shingles need a pitch of at least 2/12 under the International Residential Code (R905.2.2). From 2/12 up to 4/12, the code calls for two layers of underlayment.
Method and sources
Each calculator uses the standard formula and the manufacturer's own figures, such as bag yields, and rounds up where running short would cost you a trip. Every step is shown. Cost ranges come from named surveys with the date we checked them. Spot something wrong? Tell us and we will fix it and note the change.
- Pitch is rise in inches per 12 inches of horizontal run (NRCA).
- Pitch factor = square root of (1 + (rise / 12) squared).
- Shingle limits from IRC R905.2.2: 2/12 minimum; double underlayment below 4/12.