Roof Pitch Calculator
Enter rise and run, or the angle, and get your roof pitch as x/12, degrees and slope percent. Add the building width to get rafter length and ridge height.
Roof pitch chart
Common pitches with their angle, slope percentage and the factor that converts floor area to roof area.
| Pitch | Angle | Slope % | Multiplier | Type |
|---|---|---|---|---|
| 1/12 | 4.8° | 8.3% | 1.003 | Flat / low slope |
| 2/12 | 9.5° | 16.7% | 1.014 | Low slope |
| 3/12 | 14.0° | 25.0% | 1.031 | Low slope |
| 4/12 | 18.4° | 33.3% | 1.054 | Conventional |
| 5/12 | 22.6° | 41.7% | 1.083 | Conventional |
| 6/12 | 26.6° | 50.0% | 1.118 | Conventional |
| 7/12 | 30.3° | 58.3% | 1.158 | Conventional |
| 8/12 | 33.7° | 66.7% | 1.202 | Conventional |
| 9/12 | 36.9° | 75.0% | 1.250 | Steep |
| 10/12 | 39.8° | 83.3% | 1.302 | Steep |
| 11/12 | 42.5° | 91.7% | 1.357 | Steep |
| 12/12 | 45.0° | 100.0% | 1.414 | Very steep |
| 13/12 | 47.3° | 108.3% | 1.474 | Very steep |
| 14/12 | 49.4° | 116.7% | 1.537 | Very steep |
| 15/12 | 51.3° | 125.0% | 1.601 | Very steep |
| 16/12 | 53.1° | 133.3% | 1.667 | Very steep |
| 17/12 | 54.8° | 141.7% | 1.734 | Very steep |
| 18/12 | 56.3° | 150.0% | 1.803 | Very steep |
How to measure roof pitch
From the attic. Mark 12 inches along a level held against the bottom of a rafter. Measure straight up from that mark to the rafter. The inches you measure are the rise, so 7 inches means a 7/12 pitch.
On the roof. Lay a 2-foot level on the shingles with one end touching. Mark 12 inches along it and measure down to the roof surface. Only do this on a dry, walkable roof.
From the ground. Use a phone level app or a speed square lined up with the gable edge to read the angle, then switch the calculator to degrees.
Pitch, slope and angle
Roofers in the US write pitch as rise over a 12-inch run, like 6/12. Slope percent is the same ratio times 100, so 6/12 is 50%. The angle in degrees is the arctangent of rise ÷ run.
The area multiplier tells you how much bigger the roof surface is than the floor below. Multiply your footprint by it to get roof square footage, then divide by 100 to get squares.
Roof pitch questions
What does a 4/12 roof pitch mean?
The roof rises 4 inches for every 12 inches it runs horizontally. That is an angle of about 18.4 degrees, a fairly low slope that is common on ranch houses.
What is the most common roof pitch?
Most US houses fall between 4/12 and 9/12. A 6/12 pitch (26.6 degrees) is a typical middle value and is still walkable for most roofers.
What is the minimum pitch for asphalt shingles?
Manufacturers generally allow shingles down to 2/12 with special double underlayment, and 4/12 and up with standard underlayment. Below 2/12 you need a membrane such as TPO or EPDM.
How do I convert roof pitch to degrees?
Divide the rise by 12 and take the arctangent. For a 9/12 pitch, arctan(9 ÷ 12) = 36.9 degrees. The chart on this page lists every pitch from 1/12 to 18/12.
Can I measure roof pitch from the ground?
Yes, roughly. Stand back, hold a phone level app or a speed square in line with the roof edge on a gable end, and read the angle. Then enter it in degrees above.