Quick answer: Roof pitch is the rise in inches per 12 inches of run (e.g., 6/12). Divide the rise by the run and multiply by 12 for the pitch, or take the arctangent of rise ÷ run for the angle in degrees.
Enter your roof's rise and run to instantly find the pitch, angle in degrees, percentage grade, and the rafter slope multiplier.
Rafter length is the sloped distance (line length), before adding overhang or subtracting half the ridge thickness. For full cut lengths use the Roof Rafter Length Calculator.
Roof pitch describes how steep a roof is. In the US it is written as rise-in-run — the number of inches a roof rises vertically for every 12 inches it runs horizontally. A "6/12 pitch" (spoken "six twelve") rises 6 inches for every 12 inches of horizontal run. The run is almost always fixed at 12, so the pitch is really just the rise.
This calculator takes your measured rise and run and converts it into the four numbers builders actually use:
The most common residential pitches, with their angle in degrees, percentage grade, and slope multiplier. Use this as a quick reference for converting any standard pitch.
| Pitch (x/12) | Angle (degrees) | Grade (%) | Slope Multiplier |
|---|---|---|---|
| 1 / 12 | 4.76° | 8.3% | 1.0035 |
| 2 / 12 | 9.46° | 16.7% | 1.0138 |
| 3 / 12 | 14.04° | 25.0% | 1.0308 |
| 4 / 12 | 18.43° | 33.3% | 1.0541 |
| 5 / 12 | 22.62° | 41.7% | 1.0833 |
| 6 / 12 | 26.57° | 50.0% | 1.1180 |
| 7 / 12 | 30.26° | 58.3% | 1.1577 |
| 8 / 12 | 33.69° | 66.7% | 1.2019 |
| 9 / 12 | 36.87° | 75.0% | 1.2500 |
| 10 / 12 | 39.81° | 83.3% | 1.3017 |
| 11 / 12 | 42.51° | 91.7% | 1.3566 |
| 12 / 12 | 45.00° | 100.0% | 1.4142 |
You do not need to climb onto the roof. The safest method uses a level and a tape measure in the attic or against a gable end:
If you can only measure a different run (say the level is 24 inches), enter your actual rise and run above and the calculator normalizes it to the standard /12 pitch for you.
We keep four separate roof-pitch pages because people arrive with four different questions. If this is not the one you wanted:
A 4/12 pitch equals 18.43°. It rises 4 inches for every 12 inches of horizontal run, which is a 33.3% grade with a slope multiplier of 1.054.
Measure the vertical rise over a 12-inch horizontal run. The pitch is simply that rise written as "rise/12". To get the angle, take the arctangent of rise divided by run and convert to degrees — exactly what this calculator does automatically.
The roof pitch (slope) multiplier converts a flat, measured-from-the-ground area into the actual sloped surface area of the roof. Because a sloped roof is longer than its horizontal footprint, multiplying the plan area by this factor gives you the true area for ordering shingles, underlayment, or metal panels.
For shingle roofs in most climates, 4/12 to 8/12 is the sweet spot — steep enough to shed water and snow, but still walkable and economical. In heavy-snow regions a steeper pitch sheds load faster; in hot, dry regions low slopes are common.
Divide the rise by the run and multiply by 100. A 6/12 pitch is 6 ÷ 12 × 100 = 50%.
Last reviewed August 2026 · how we source these figures
Every constant this calculator uses and where it comes from, so you can check it rather than take our word for it.
Local codes amend the model IRC and adopt different cycles — your building department governs. Manufacturers revise yields; where your product's data sheet disagrees with a default here, use the product's number. See our full methodology.