Pitch tells you how steep a roof is, which decides the roofing material you can use, the length of every rafter, and how much surface you will be covering. Enter any rise and run — for example, hold a level 12" out from the roof and measure straight down to the surface — and the calculator converts it to every common format.
Pitch, angle and slope
- Pitch is rise per 12 units of run: 6:12 means 6" of rise for every 12" horizontally.
- Angle is arctan(rise ÷ run). 6:12 is 26.57°.
- Slope as a percentage is rise ÷ run × 100. 6:12 is 50%.
- Rafter multiplier is √(1 + (rise ÷ run)²). Multiply plan area or horizontal run by it to get the sloped length or area.
Common pitches
| Pitch | Angle | Multiplier | Notes |
|---|---|---|---|
| 3:12 | 14.04° | 1.031 | Low slope, double underlayment |
| 4:12 | 18.43° | 1.054 | Common ranch roofs |
| 6:12 | 26.57° | 1.118 | Typical suburban gable |
| 8:12 | 33.69° | 1.202 | Walkable with care |
| 12:12 | 45.00° | 1.414 | Steep; staging required |
Worked example
A house footprint with overhangs measures 1,200 ft² and the pitch is 6:12. Roof area = 1,200 × 1.118 ≈ 1,342 ft², or 13.4 roofing squares (one square = 100 ft²). Add 10–15% for waste, hips and starter courses when ordering shingles.
Watch: how it is done
Video by Digital Roofing Innovations on YouTube. More in our video library.
Frequently asked questions
What is the most common roof pitch?
In North American houses, 4:12 to 9:12 covers most roofs, with 6:12 being very common.
What is the minimum pitch for asphalt shingles?
Most manufacturers require at least 2:12, with special underlayment between 2:12 and 4:12. Below that, use a low-slope membrane.
How do I measure pitch from inside the attic?
Hold a level horizontally against the underside of a rafter, mark 12" along the level, and measure vertically from that mark up to the rafter. That number is the rise per 12.
Results are planning estimates. For structural work, confirm requirements with your local building authority and a qualified professional. See our disclaimer.