Common roof pitches
| Degrees | Ratio (x:12) | Percent | Pitch factor |
|---|---|---|---|
| 5° | 1.0:12 | 9% | 1.004 |
| 10° | 2.1:12 | 18% | 1.015 |
| 15° | 3.2:12 | 27% | 1.035 |
| 20° | 4.4:12 | 36% | 1.064 |
| 22.5° | 5.0:12 | 41% | 1.082 |
| 25° | 5.6:12 | 47% | 1.103 |
| 30° | 6.9:12 | 58% | 1.155 |
| 35° | 8.4:12 | 70% | 1.221 |
| 40° | 10.1:12 | 84% | 1.305 |
| 45° | 12.0:12 | 100% | 1.414 |
Pitch factor turns a flat plan area into the real, sloping roof area. It’s what you need to estimate roofing sheets, tiles, sarking or paint.
Stay off the roof
Working on a roof is high-risk. In Australia, many roof jobs also involve licensed work, such as roof plumbing (gutters and downpipes connected to stormwater) and anything electrical like solar. For gutters, see how to clean gutters safely.
Questions
How do I convert roof pitch to degrees?
Degrees = tan⁻¹(rise ÷ run). A 6:12 pitch (6 up for every 12 across) is 26.6°, and a 22.5° roof rises about 414 mm per metre.
What is a common roof pitch in Australia?
Australian homes are usually described in degrees: 22.5° is very common for tiled roofs, with lower pitches of 5–15° typical for metal skillion and flat-look roofs. Minimum pitches depend on the roofing product, so check the manufacturer’s specifications.
How do I work out the actual roof area from the floor plan?
Multiply the plan area (including eaves) by the pitch factor, 1 ÷ cos(pitch). For a 22.5° roof that’s about 1.08, so a 200 m² plan area has roughly 216 m² of roof surface.
Is roof pitch the same as slope percentage?
They describe the same thing differently. Percentage = rise ÷ run × 100, so a 22.5° roof is about a 41% slope, and 45° is 100%.
Estimates only. Check the product label and your measurements before you buy. More free tools: see them all.