Roof pitch formulas
Pitch is the rise of a roof for every 12 inches of horizontal run. Every value this calculator shows comes from the same right triangle.
Degrees = arctan(rise / 12) x 180 / π
Percent slope = rise / 12 x 100
Pitch factor = √(1 + (rise / 12)²)
Example: a roof that rises 7 feet over a 14 foot rafter run is 12 x 7 / 14 = 6/12, which is 26.57° and 50% slope.
Common pitches at a glance
| Pitch | Degrees | Percent slope | Pitch factor |
|---|---|---|---|
| 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 |
| 12/12 | 45.00° | 100.0% | 1.414 |
Every pitch from 1/12 to 24/12 is in the full roof pitch chart.
Want a pro to confirm these numbers?
Numbers look right? A licensed roofer can measure on site and give you an exact price.
How to measure roof pitch
- From the attic. Hold a level flat against the underside of a rafter. Mark 12 inches on the level, then measure straight down to the rafter. That number is the rise.
- On the roof. Set a level on the shingles with one end touching. Measure from the level's 12 inch mark down to the roof surface.
- From the ground. Hold a phone inclinometer app on the gable trim, read the angle, then switch the calculator to degrees.
Why pitch matters
- Material. Standard asphalt shingles need at least 4/12. From 2/12 to 4/12 they need double underlayment. Below 2/12, use a membrane or standing seam metal.
- Material quantity. Multiply plan area by the pitch factor before ordering. The roof square footage calculator does this.
- Labor. Above about 7/12, roofers add safety gear and charge more.
- Framing. Pitch sets the plumb and seat cut angles on every rafter.
Sources and further reading
- 2021 International Residential Code, Chapter 9: Roof Assemblies
- 2021 International Residential Code, Chapter 8: Roof-Ceiling Construction
- National Roofing Contractors Association (NRCA)
Frequently asked questions
What is the most common roof pitch?
In the US, 6/12 is the most common residential pitch. Most homes fall between 4/12 and 9/12.
How do I convert roof pitch to degrees?
Take the arctangent of rise divided by 12. A 6/12 pitch is arctan(0.5) = 26.57 degrees. The pitch to degrees table lists every common pitch.
Is roof pitch the same as roof slope?
In everyday use, yes. Both usually mean rise per 12 inches of run. Engineers sometimes write slope as a percent, so a 6/12 pitch is a 50% slope.
What is the pitch factor?
It is the number you multiply flat (plan) area by to get the real sloped roof area. At 6/12 it is 1.118, so 1,000 sq ft of plan area is 1,118 sq ft of roof.
What is the minimum pitch for shingles?
2/12 with special low-slope underlayment, and 4/12 for a standard installation. Check the shingle maker's instructions, which control the warranty.