8/12 Roof Pitch: Angle, Multiplier and What It Means
Angle
33.7 degrees
8 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.
- Rise8 in per 12 in run
- Footprint area, 0 to skip1200 sq ft
Slope multiplier1.2 x footprint
At 8/12 and above the crew needs roof jacks or staging, and the labor rate goes up with it.
| Pitch | 8/12 |
|---|---|
| Slope multiplier | 1.2 xmultiply footprint by this |
| Angle | 33.7 degrees |
| Grade | 66.7% |
| Rafter length per 12 ft of run | 14.42 ft |
| Roof surface for 1,200 sq ft footprint | 1,442 sq ft |
| That is | 14.4 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
An 8/12 pitch is 33.7 degrees and a two thirds grade. Nobody walks this unstaged. Roof jacks, planks and fall protection are the working assumption, and a bid that does not carry the labor for setting and moving them is a bid that loses money.
The multiplier is a round 1.2, so the roof surface is a fifth larger than the footprint: 1,200 square feet on the plan is 1,442 square feet on the roof, 14.4 squares. That twenty percent is the single biggest reason footprint based estimates go wrong on steep houses.
The payoff is attic volume. An 8/12 over a 28 foot span puts the ridge more than nine feet above the joists, which is a real room rather than a crawl space, and it is why so many story and a half houses were built at this pitch.
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 8/12 in degrees?
33.7 degrees, which is a 66.7 percent grade.
Do I need roof jacks on an 8/12?
Yes. An 8/12 is not a walkable surface and staging is not optional at this slope.
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.