12/12 Roof Pitch: 45 Degrees, and What That Costs
Angle
45 degrees
12 inches of rise for every 12 inches of run, over a 1,200 square foot footprint.
At 8/12 and above the crew needs roof jacks or staging, and the labor rate goes up with it.
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.
- Rise12 in per 12 in run
- Footprint area, 0 to skip1200 sq ft
Slope multiplier1.41 x footprint
At 8/12 and above the crew needs roof jacks or staging, and the labor rate goes up with it.
| Pitch | 12/12 |
|---|---|
| Slope multiplier | 1.41 xmultiply footprint by this |
| Angle | 45 degrees |
| Grade | 100% |
| Rafter length per 12 ft of run | 16.97 ft |
| Roof surface for 1,200 sq ft footprint | 1,697 sq ft |
| That is | 17 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 12/12 pitch is exactly 45 degrees, because the rise equals the run. The multiplier is the square root of two, 1.41, so the roof surface is 41 percent larger than the footprint: 1,200 square feet on the plan is 1,697 square feet of roof, about 17 squares.
That 41 percent is the whole lesson of slope multipliers. Somebody who prices a 12/12 house off the floor plan is short by more than four squares of material and short by the labor to install it, on top of a steep slope premium they have probably also forgotten.
Roofs this steep are usually there for a reason: snow country, a specific architectural style, or full height rooms inside the roof. They shed everything, they last well, and they are expensive to work on twice, so it is worth putting the better underlayment on while the staging is already up.
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
What is a 12/12 pitch in degrees?
Exactly 45 degrees, because the rise and the run are the same. It is a 100 percent grade.
How much more material does a 12/12 roof need?
41 percent more than the flat footprint, since the slope multiplier is 1.41. On a 1,200 square foot footprint that is about 5 extra squares.
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.