4/12 Roof Pitch: Angle, Multiplier and What It Means
Angle
18.4 degrees
4 inches of rise for every 12 inches of run, over a 1,200 square foot footprint.
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.
- Rise4 in per 12 in run
- Footprint area, 0 to skip1200 sq ft
Slope multiplier1.05 x footprint
| Pitch | 4/12 |
|---|---|
| Slope multiplier | 1.05 xmultiply footprint by this |
| Angle | 18.4 degrees |
| Grade | 33.3% |
| Rafter length per 12 ft of run | 12.65 ft |
| Roof surface for 1,200 sq ft footprint | 1,265 sq ft |
| That is | 12.6 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 4/12 pitch is 18.4 degrees and the point where a roof stops being a low slope application. From 4/12 up, asphalt shingles go on with a single underlayment layer under the standard instructions, which is why so many tract houses land exactly here.
The multiplier is 1.05, so a 1,200 square foot footprint is 1,265 square feet of roof, about 12.6 squares. That five percent is the difference between ordering off the plan and ordering off the roof, and it is the most common reason a shingle order comes up short.
It walks easily and it is the last pitch most crews will work without roof jacks. Above it, staging goes up, the day gets slower, and the price per square starts to move.
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 4/12 in degrees?
18.4 degrees, which is a 33.3 percent grade.
Is 4/12 a good roof pitch?
It is the most common residential pitch in the United States. It sheds water well, takes standard shingle installation with a single underlayment, and is still safe to walk.
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.