4/12 Pitch in Degrees (18.43°) and a Roof Pitch Converter
Updated · By the Roof to Footing editors
A 4/12 pitch is 18.43 degrees. The roof rises 4 inches for every 12 inches it runs horizontally, which works out to a 33.3% grade, and the roof surface is about 5.4% larger than the flat area under it (a pitch multiplier of 1.054). It's one of the most common pitches on American ranch houses and porch roofs.
The math
Pitch is a ratio of rise to run. To turn it into an angle, take the arctangent:
degrees = arctan(rise ÷ 12)
For 4/12: arctan(4 ÷ 12) = arctan(0.3333) = 18.43°.
Going the other way, rise = tan(angle) × 12. So a 30° roof is tan(30°) × 12 = 6.93, or roughly a 7/12 pitch.
Roof pitch to degrees converter
4/12 = 18.43°, 33.3% grade, multiplier 1.054
30° = 6.93/12 pitch
| Pitch | Degrees | Grade | Multiplier |
|---|---|---|---|
| 1/12 | 4.76° | 8.3% | 1.003 |
| 2/12 | 9.46° | 16.7% | 1.014 |
| 3/12 | 14.04° | 25.0% | 1.031 |
| 4/12 | 18.43° | 33.3% | 1.054 |
| 5/12 | 22.62° | 41.7% | 1.083 |
| 6/12 | 26.57° | 50.0% | 1.118 |
| 7/12 | 30.26° | 58.3% | 1.158 |
| 8/12 | 33.69° | 66.7% | 1.202 |
| 9/12 | 36.87° | 75.0% | 1.250 |
| 10/12 | 39.81° | 83.3% | 1.302 |
| 11/12 | 42.51° | 91.7% | 1.357 |
| 12/12 | 45.00° | 100.0% | 1.414 |
What a 4/12 pitch means in practice
- Walkable. Most people can walk a 4/12 roof in dry weather with soft-soled shoes. Roofers generally consider anything above about 6/12 steep enough to need roof jacks or harnesses for everyday work. Use fall protection anyway.
- Shingles are fine. Asphalt (composition) shingles need at least 2/12 with double underlayment, and 4/12 is the point where standard single-layer underlayment is allowed under the IRC. See our guide to the composition roof.
- Metal is fine. 4/12 is above the 3/12 minimum for exposed-fastener metal panels and for snap lock standing seam. Details are in minimum pitch for a metal roof.
- Attic space is modest. On a 28-foot-wide house, a 4/12 roof peaks about 4 feet 8 inches above the ceiling joists at the center, enough for storage and insulation but not a room.
Using the pitch multiplier
Roofers quote by the square (100 square feet of roof surface), not by the footprint. Multiply the roof's flat footprint, including overhangs, by the pitch multiplier to get the real surface area.
Example: a house with a 2,000-square-foot roof footprint at 4/12 has 2,000 × 1.054 = 2,108 square feet of roof, or about 21 squares before waste.
Measuring pitch without climbing
From the attic, hold a level against the underside of a rafter so it's horizontal. Mark 12 inches along the level, then measure straight up to the bottom of the rafter. That measurement is the rise. Phone apps that read pitch from a photo of the gable or from the phone laid on a rafter are close enough for planning, but measure before you order materials.