7/12 roof pitch in degrees
A 7/12 roof pitch is 30.2564°. That is a 58.33% grade, a slope ratio of 1 : 1.7143, and a rafter factor of 1.157704, and the angle is irrational so it carries the ≈.
Change the pitch
30.2564°≈
Multiply your run by 1.157704 for the rafter length. The cuts and the birdsmouth are in the app.
Rafter length at 7/12, by span
Run is half the span on a symmetrical gable. Length is along the rafter, before any birdsmouth, ridge or tail is taken off.
| Building span | Run | Rafter length | Decimal feet |
|---|---|---|---|
| 20 ft | 10 ft | 11' 6-15/16" | 11.577 ft |
| 24 ft | 12 ft | 13' 10-11/16" | 13.892 ft |
| 28 ft | 14 ft | 16' 2-1/2" | 16.208 ft |
| 32 ft | 16 ft | 18' 6-1/4" | 18.523 ft |
| 36 ft | 18 ft | 20' 10-1/16" | 20.839 ft |
Every row is the run multiplied by 1.157704, the rafter factor for 7/12. The same figure for every pitch is on the full roof pitch chart.
What 7/12 means on the roof
Seven in twelve is the closest any whole-number pitch comes to a round 30°, at 30.2564°, and it is the one crews argue about. Six is walkable and eight is not, so 7/12 is where the boots-or-jacks decision actually gets made, and two roofers will price the same roof differently because of it.
The working is the arctangent of the rise over the run: atan(7 ÷ 12) = 30.2564°. The rafter factor is the hypotenuse of the same triangle over its base, √(12² + 7²) ÷ 12, which is why multiplying any run by 1.157704 gives the rafter. That figure is the roof pitch multiplier, and it is the same number whatever the size of the roof.
Shingle slope limits quoted here are from the IRC, the United States model code. Your state, province or county may amend them, and several do.
