2/12 Roof Pitch: Angle, Multiplier and What It Means
Angle
9.5 degrees
2 inches of rise for every 12 inches of run, over a 1,200 square foot footprint.
Between 2/12 and 4/12 most shingle manufacturers require a doubled underlayment or the warranty is void.
How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Rise2 in per 12 in run
- Footprint area, 0 to skip1200 sq ft
Slope multiplier1.01 x footprint
Between 2/12 and 4/12 most shingle manufacturers require a doubled underlayment or the warranty is void.
| Pitch | 2/12 |
|---|---|
| Slope multiplier | 1.01 xmultiply footprint by this |
| Angle | 9.5 degrees |
| Grade | 16.7% |
| Rafter length per 12 ft of run | 12.17 ft |
| Roof surface for 1,200 sq ft footprint | 1,217 sq ft |
| That is | 12.2 squares |
Pitch compared
The whole table, so you do not have to come back for the next one.
| Pitch | Slope multiplier | Angle | Grade |
|---|---|---|---|
| 2/12 | 1.01 x footprint | 9.5 degrees | 16.7% |
| 3/12 | 1.03 x footprint | 14 degrees | 25% |
| 4/12 | 1.05 x footprint | 18.4 degrees | 33.3% |
| 5/12 | 1.08 x footprint | 22.6 degrees | 41.7% |
| 6/12 | 1.12 x footprint | 26.6 degrees | 50% |
| 7/12 | 1.16 x footprint | 30.3 degrees | 58.3% |
| 8/12 | 1.2 x footprint | 33.7 degrees | 66.7% |
| 9/12 | 1.25 x footprint | 36.9 degrees | 75% |
| 10/12 | 1.3 x footprint | 39.8 degrees | 83.3% |
| 12/12 | 1.41 x footprint | 45 degrees | 100% |
What else matters here
A 2/12 pitch is 9.5 degrees, which is barely a slope at all. It is the absolute floor for asphalt shingles under the IRC, and only with a doubled underlayment application: below 2/12 shingles are not permitted at any price and the roof has to be a membrane.
Because the slope is so shallow, the multiplier is only 1.01, so the roof surface is barely larger than the footprint. What you save in material you pay for in detailing, since water moves slowly on a 2/12 and any lap that is short or any fastener that is high will find its way through.
Low slope is also where ice dams do their worst work in cold climates. Ice and water shield well up from the eave, and generous ventilation, matter more here than on any steep roof.
What this calculator assumes
- Pitch is written as rise over a 12 inch run. A 6/12 roof climbs 6 inches for every 12 inches across.
- The slope multiplier converts flat footprint area into real roof surface. It is the number that decides whether you order enough shingles.
- Below 2/12, shingles are not rated. Below 4/12, most manufacturers require a double underlayment. Over 8/12 you are on roof jacks and the labor price changes.
Questions people ask
Can you put shingles on a 2/12 pitch?
Yes, but it is the minimum the IRC allows and it requires a doubled underlayment application. Below 2/12 asphalt shingles are not permitted and you need a low slope membrane instead.
What is 2/12 in degrees?
9.5 degrees, which is a 16.7 percent grade.
What is the slope multiplier for?
Multiply the flat footprint of the building by it to get the real surface area of the roof. A roof plan gives you the footprint, and the multiplier turns it into the area you actually have to cover.
The roof pitch calculator takes any dimensions you like and hands back the same list.