10/12 Roof Pitch: Angle, Multiplier and What It Means
Angle
39.8 degrees
10 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.
- Rise10 in per 12 in run
- Footprint area, 0 to skip1200 sq ft
Slope multiplier1.3 x footprint
At 8/12 and above the crew needs roof jacks or staging, and the labor rate goes up with it.
| Pitch | 10/12 |
|---|---|
| Slope multiplier | 1.3 xmultiply footprint by this |
| Angle | 39.8 degrees |
| Grade | 83.3% |
| Rafter length per 12 ft of run | 15.62 ft |
| Roof surface for 1,200 sq ft footprint | 1,562 sq ft |
| That is | 15.6 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 10/12 pitch is 39.8 degrees, close enough to 40 that it reads as a wall from the ground. The multiplier is 1.3, so 1,200 square feet of footprint is 1,562 square feet of roof, 15.6 squares, and nearly a third more of everything that covers it.
On a roof this steep the labor is set by access, not by area. Jack spacing gets tighter, the crew moves slower, material has to be staged in small lots, and a windy day simply stops the work. Price the staging honestly or the job eats the margin.
Check the underlayment and fastener requirements for whatever covering is going on. Some products have different nailing patterns above a certain slope, and on a steep roof a pattern that is only nearly right will show itself in the first hard wind.
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 10/12 in degrees?
39.8 degrees, which is an 83.3 percent grade.
Can you walk a 10/12 roof?
No. A 10/12 is a staged roof. Jacks, planks and fall protection are the only way it gets worked safely.
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.