Keep this page open while you stand in the attic with a tape. Roof pitch is written as rise over run, with run always fixed at 12 in. Once you have the rise, the angle and the percent grade fall straight out of the table below.
How pitch is written
A roof marked 6/12 rises 6 in for every 12 in of horizontal travel. The first number is the rise, the second is the fixed run of 12 in. Pitch is never written as a decimal or a fraction on its own; the /12 is the whole point.
Measure it in 30 seconds
In the attic, rest a straight level on a rafter. Measure 12 in along the level from the wall end and make a mark. Then drop a tape measure straight down from that mark to the rafter below. The number you read is your rise over 12. On a finished roof, the same trick works from the ground with a gauge, but the attic is easier.
Quick reference table
| Pitch | Degrees | Grade | Typical use |
|---|---|---|---|
| 2/12 | 9.5° | 17% | Low slope, needs membrane |
| 4/12 | 18.4° | 33% | Sheds and modern homes |
| 6/12 | 26.6° | 50% | Common suburban roof |
| 8/12 | 33.7° | 67% | Traditional steep roofs |
| 12/12 | 45° | 100% | Cape Cod style |
Reading the table
6/12 sits at about 26.6 degrees and a 50 percent grade. That 50 percent figure is the same number a hiker sees on a trail sign, so it is an easy way to picture the slope. 8/12 is closer to 34 degrees, and 12/12 is a true 45-degree roof.
Why pitch matters downstream
Pitch decides how many shingles you need, because a steeper roof has more surface area over the same footprint. It also sets rafter length and whether the roof is walkable. Below 4/12, treat it as a low-slope roof and use rolled membrane instead of standard shingles.
Walkability and safety
Below 4/12, a boot does not bite, and contractors use roof brackets and harnesses. Above 8/12, even a skilled roofer ties off, because the slope outruns the friction of a work boot. The sweet spot for maintenance is 4/12 to 8/12, where you can stand and shovel snow without gear. If you are ordering shingles, remember that steeper roofs need more surface area, so feed the pitch number into the shingle calculator next.
Worked example
6 in rise over 12 in run gives 6/12, about 26.6 degrees, and a 50 percent grade. That is the number to plug into the shingle and rafter tools next.
Roof Pitch Calculator
A 6 in rise over 12 in of run is 6/12, about 26.6 degrees, and a 50 percent grade, and the table below converts the rest.
How to use
- Find a rafter in the attic or hold a level on the roof
- Mark 12 in of horizontal run
- Measure the vertical rise over that run
- Read pitch as rise over 12, plus degrees and percent
Supported formats and limits
- Residential pitches usually run from 4/12 to 12/12
- Anything flatter than 2/12 needs special roofing membrane
- Anything steeper than 10/12 is hard to walk on
Examples
6 in of rise over 12 in of run equals 6/12, about 26.6 degrees, and a 50 percent grade.Common errors
- Rise must be a positive number of inches
- Run is assumed to be 12 in for pitch notation
Privacy and browser support
All conversions run locally in your browser. No roof measurements are uploaded.
FAQ
What does 6/12 mean?
The roof rises 6 inches for every 12 inches it runs horizontally. It is the most common suburban pitch, near 26.6 degrees and a 50 percent grade.
How do I measure pitch from the attic?
Hold a level against a rafter. Mark 12 in along the level from the end, then measure straight down to the rafter. That vertical number is the rise over 12.
How do I convert pitch to degrees?
4/12 is near 18 degrees, 6/12 near 26.6 degrees, 8/12 near 33.7 degrees, and 12/12 is a full 45 degrees.
What is the minimum walkable pitch?
4/12. Below that, roof brackets and fall protection are required, because feet slide on lower slopes.
Does pitch affect shingles?
Low roofs need double underlayment because water stands longer. Steep roofs shed fast but need harnesses to work on.
What is percent grade?
Rise divided by run as a percentage. 6/12 is 50 percent, 12/12 is 100 percent, and 4/12 is about 33 percent.