Roof Pitch Calculator
Convert a roof pitch between X/12, degrees, percent slope and measured rise over run, and see the slope multipliers used elsewhere on the site.
Calculate
Results
Draft — press Calculate| As X/12 | 6 / 12 |
|---|---|
| Degrees | 26.565° |
| Percent slope | 50% |
| Area / common multiplier | 1.118 |
| Hip multiplier | 1.5 |
Pitch describes how steep a roof is. In the United States it is usually written as X/12: the inches of vertical rise for every 12 inches of horizontal run. The same slope can be written as an angle in degrees or as a percentage. These are different units, and a frequent mistake is to read a percentage as an angle. A 6/12 pitch is a 50 percent slope but only about 26.57 degrees.
X/12, degrees and percent
The slope ratio p equals X/12 and also equals the tangent of the angle. So the angle is arctan(p), and the percent slope is 100 × p. The area and common-rafter multiplier is √(1 + p²); the hip multiplier is √(2 + p²). Those multipliers are exactly what the area and rafter tools use, so a pitch entered here behaves identically everywhere.
Pitch chart from 1/12 to 12/12
The table below is generated from the same engine the calculators use. It lists the angle, percent slope and the two multipliers for each whole pitch.
| Pitch | Angle | Percent | Area multiplier | Hip multiplier |
|---|---|---|---|---|
| 1/12 | 4.76° | 8.3% | 1.003 | 1.417 |
| 2/12 | 9.46° | 16.7% | 1.014 | 1.424 |
| 3/12 | 14.04° | 25% | 1.031 | 1.436 |
| 4/12 | 18.43° | 33.3% | 1.054 | 1.453 |
| 5/12 | 22.62° | 41.7% | 1.083 | 1.474 |
| 6/12 | 26.57° | 50% | 1.118 | 1.5 |
| 7/12 | 30.26° | 58.3% | 1.158 | 1.53 |
| 8/12 | 33.69° | 66.7% | 1.202 | 1.563 |
| 9/12 | 36.87° | 75% | 1.25 | 1.601 |
| 10/12 | 39.81° | 83.3% | 1.302 | 1.641 |
| 11/12 | 42.51° | 91.7% | 1.357 | 1.685 |
| 12/12 | 45° | 100% | 1.414 | 1.732 |
Measuring pitch and one example
To measure pitch, hold a level horizontally against the roof, measure 12 inches along it, then measure straight down to the roof surface; that drop in inches is the X in X/12. Example: a measured rise of 5 inches over a 12-inch run is a 5/12 pitch, about 22.62 degrees and a 41.67 percent slope, with an area multiplier of about 1.0833. Which slopes suit which covering is a manufacturer and local-code question, not a geometry one.
Frequently Asked Questions
Is 50% slope the same as 50 degrees?
No. Percent slope is 100 times the rise-over-run ratio, while degrees come from the arctangent of that ratio. A 50 percent slope (6/12) is about 26.57 degrees.
What is the slope multiplier?
It is √(1 + p²), the factor that converts a plan footprint into sloped surface area and a run into a common rafter length. The hip multiplier √(2 + p²) does the same for diagonal hip rafters.