Find your roof pitch in seconds. Enter the rise and run (or the angle) and this roof pitch calculator shows the pitch in x/12, the angle in degrees, the slope percentage and the rafter multiplier.
What is roof pitch?
Roof pitch is how many inches a roof rises for every 12 inches of horizontal run. A 6/12 roof rises 6 inches for every 12 inches across.
Pitch = (Rise ÷ Run) × 12 | Angle = arctan(Rise ÷ Run)
How to measure roof pitch
- Mark 12 inches on a level.
- Place one end of the level on the roof (or the underside of a rafter) and hold it level.
- Measure straight up from the 12-inch mark to the roof surface. That number is the rise, so a 5-inch measurement means a 5/12 pitch.
Roof pitch angles chart
| Pitch | Angle | Rafter multiplier |
|---|---|---|
| 1/12 | 4.76° | 1.003 |
| 2/12 | 9.46° | 1.014 |
| 3/12 | 14.04° | 1.031 |
| 4/12 | 18.43° | 1.054 |
| 5/12 | 22.62° | 1.083 |
| 6/12 | 26.57° | 1.118 |
| 7/12 | 30.26° | 1.158 |
| 8/12 | 33.69° | 1.202 |
| 9/12 | 36.87° | 1.250 |
| 10/12 | 39.81° | 1.302 |
| 11/12 | 42.51° | 1.357 |
| 12/12 | 45.00° | 1.414 |
Pitch vs. slope vs. angle
Pitch is written as rise over 12 (6/12). Slope is often written as a percentage (6/12 = 50%). The angle is measured in degrees from horizontal (6/12 ≈ 26.57°). They all describe the same steepness.
What is the rafter multiplier?
Multiply the horizontal run (or the flat footprint area) by this number to get the actual sloped length or roof area. For a 6/12 roof, a 12-foot run needs a rafter about 12 × 1.118 = 13.4 ft long, before overhang.
Frequently asked questions
What is the most common roof pitch?
Pitches between 4/12 and 9/12 are common on houses. Low-slope roofs (below 4/12) usually need special underlayment or roofing materials, so check the manufacturer’s requirements.
What angle is a 4/12 pitch?
About 18.43 degrees.