What does roof pitch mean?
Roof pitch describes how much a roof rises compared with its horizontal run. In the United States, it is commonly written as x:12 or x/12. A 6:12 pitch, also written 6/12, rises 6 inches for every 12 inches of horizontal run. The same slope can also be written as 26.6° or 50%.
How to use this roof pitch calculator
Choose the pitch format you already know, enter one value or a rise-and-run pair, and calculate. Need Materials converts that slope into the other common formats and calculates the pitch multiplier used for roof area. Do not enter the sloped rafter length as the run: run is horizontal.
How to measure roof pitch without climbing onto the roof
Use building plans, an existing roof report or an attic measurement when possible. From an accessible attic, pitch can be measured as vertical rise over a level horizontal run. Do not climb onto a roof to take measurements without appropriate training and fall protection. If the measurement is uncertain or the roof is complex, use a professional roof report.
Roof pitch conversions
All four values describe the same slope. The calculator first converts the input to rise divided by run, then derives x:12, degrees, percent and the area multiplier.
slope ratio = rise ÷ runx:12 rise = slope ratio × 12angle = arctan(slope ratio)slope percent = slope ratio × 100pitch multiplier = √(1 + slope ratio²)
Common roof pitches and multipliers
| Pitch | Angle | Slope | Multiplier |
|---|---|---|---|
| 0:12 | 0.0° | 0.0% | 1.0000 |
| 2:12 | 9.5° | 16.7% | 1.0138 |
| 3:12 | 14.0° | 25.0% | 1.0308 |
| 4:12 | 18.4° | 33.3% | 1.0541 |
| 5:12 | 22.6° | 41.7% | 1.0833 |
| 6:12 | 26.6° | 50.0% | 1.1180 |
| 8:12 | 33.7° | 66.7% | 1.2019 |
| 10:12 | 39.8° | 83.3% | 1.3017 |
| 12:12 | 45.0° | 100.0% | 1.4142 |
| 18:12 | 56.3° | 150.0% | 1.8028 |
| 21:12 | 60.3° | 175.0% | 2.0156 |
Rounded values are shown for reference. Calculations use unrounded values.
Example: convert a 6:12 roof pitch
A 6:12 pitch has a slope ratio of 6 ÷ 12 = 0.5. Its angle is arctan(0.5) = 26.6°, its slope is 50%, and its pitch multiplier is √(1 + 0.5²) = 1.1180. A 1,200 sq ft horizontal projection at this pitch has about 1,341.6 sq ft of sloped surface area.
Pitch limits for asphalt shingles
Pitch conversion is geometry, not approval for a roofing product. Slopes below 2:12 are generally outside the intended range of asphalt shingles. Slopes from 2:12 to below 4:12 require special attention to underlayment and installation. Very steep slopes can require additional fastening or hand-sealing. The product instructions and applicable code always take priority.
Frequently asked questions
What is a 6:12 roof pitch in degrees?
A 6:12 pitch is approximately 26.6°. It also equals a 50% slope and has a pitch multiplier of about 1.1180.
Is roof pitch the same as roof slope?
In common U.S. residential-roofing use, both terms often describe the same inclination, although terminology can vary. Pitch is commonly written as rise over a 12-inch run, while slope may be expressed as a percentage or ratio.
What is a roof pitch multiplier?
It converts horizontal projected area into sloped surface area. Multiply the projected area by √(1 + slope ratio²). It does not add waste or convert area into shingle bundles.
Can I calculate pitch from degrees?
Yes. Select Angle, enter the roof angle, and the calculator converts it to x:12, percent and a multiplier.
Do I need to climb onto the roof to measure pitch?
No. Use plans, a roof report or a safe attic measurement when possible. Do not climb onto a roof without appropriate training and fall protection.
Sources and review
Last reviewed:
- Method and Sources — method, assumptions and limits.
- Need Materials shared roofing domain engine — conversions and generated reference table.
- Selected roofing product instructions and applicable local code — product suitability authority.