- θ
- Pitch: the angle of the roof slope from flat, in degrees
- h
- Rise: the height from the top of the wall to the ridge
- r
- Run: from the outside of the wall to the centre line of the ridge (half the span)
- L
- Rafter length: wall to ridge along the slope, before any overhang (run × rafter factor)
- x
- Rise in 12: how far the roof rises for every 12 across (6/12 rises 6 inches per foot)
Roof pitch in degrees
| Pitch | Rise per metre of run (mm) | Rise in 12 (in per foot) | Slope (%) | Rafter factor |
|---|---|---|---|---|
| 2.5° | 44 | 0.5 | 4.4 | 1.001 |
| 5° | 87 | 1 | 8.7 | 1.004 |
| 7.5° | 132 | 1.6 | 13.2 | 1.009 |
| 10° | 176 | 2.1 | 17.6 | 1.015 |
| 12.5° | 222 | 2.7 | 22.2 | 1.024 |
| 15° | 268 | 3.2 | 26.8 | 1.035 |
| 17.5° | 315 | 3.8 | 31.5 | 1.049 |
| 20° | 364 | 4.4 | 36.4 | 1.064 |
| 22.5° | 414 | 5 | 41.4 | 1.082 |
| 25° | 466 | 5.6 | 46.6 | 1.103 |
| 27.5° | 521 | 6.2 | 52.1 | 1.127 |
| 30° | 577 | 6.9 | 57.7 | 1.155 |
| 32.5° | 637 | 7.6 | 63.7 | 1.186 |
| 35° | 700 | 8.4 | 70 | 1.221 |
| 37.5° | 767 | 9.2 | 76.7 | 1.260 |
| 40° | 839 | 10.1 | 83.9 | 1.305 |
| 42.5° | 916 | 11 | 91.6 | 1.356 |
| 45° | 1000 | 12 | 100 | 1.414 |
| 47.5° | 1091 | 13.1 | 109.1 | 1.480 |
| 50° | 1192 | 14.3 | 119.2 | 1.556 |
| 52.5° | 1303 | 15.6 | 130.3 | 1.643 |
| 55° | 1428 | 17.1 | 142.8 | 1.743 |
| 57.5° | 1570 | 18.8 | 157 | 1.861 |
| 60° | 1732 | 20.8 | 173.2 | 2.000 |
UK roof tiles and slates each have a minimum pitch: often 15° to 22.5° for interlocking tiles, 30° or more for plain tiles and many slates. Check the maker's figure, which can depend on the rafter length and how exposed the site is.
Roof pitch as a rise in 12
| Pitch | Degrees (°) | Slope (%) | Rise per metre of run (mm) | Rafter factor |
|---|---|---|---|---|
| 1/12 | 4.8 | 8.3 | 83 | 1.003 |
| 2/12 | 9.5 | 16.7 | 167 | 1.014 |
| 3/12 | 14 | 25 | 250 | 1.031 |
| 4/12 | 18.4 | 33.3 | 333 | 1.054 |
| 5/12 | 22.6 | 41.7 | 417 | 1.083 |
| 6/12 | 26.6 | 50 | 500 | 1.118 |
| 7/12 | 30.3 | 58.3 | 583 | 1.158 |
| 8/12 | 33.7 | 66.7 | 667 | 1.202 |
| 9/12 | 36.9 | 75 | 750 | 1.250 |
| 10/12 | 39.8 | 83.3 | 833 | 1.302 |
| 11/12 | 42.5 | 91.7 | 917 | 1.357 |
| 12/12 | 45 | 100 | 1000 | 1.414 |
| 13/12 | 47.3 | 108.3 | 1083 | 1.474 |
| 14/12 | 49.4 | 116.7 | 1167 | 1.537 |
| 15/12 | 51.3 | 125 | 1250 | 1.601 |
| 16/12 | 53.1 | 133.3 | 1333 | 1.667 |
| 17/12 | 54.8 | 141.7 | 1417 | 1.734 |
| 18/12 | 56.3 | 150 | 1500 | 1.803 |
| 19/12 | 57.7 | 158.3 | 1583 | 1.873 |
| 20/12 | 59 | 166.7 | 1667 | 1.944 |
| 21/12 | 60.3 | 175 | 1750 | 2.016 |
| 22/12 | 61.4 | 183.3 | 1833 | 2.088 |
| 23/12 | 62.4 | 191.7 | 1917 | 2.162 |
| 24/12 | 63.4 | 200 | 2000 | 2.236 |
US roofers give pitch as the rise in inches for every 12 inches (1 foot) across: a 6/12 roof rises 6 inches per foot of run. 12/12 is 45°.
About this chart
Roof pitches three ways: in degrees (used in the UK and Europe), as a rise in 12 (used in the US, such as 6/12) and as a percentage slope. Choose degrees or rise in 12 above the chart.
Rise per metre of run tells you how high the roof climbs for each metre across, so a 30° roof with a 4 m run rises 4 × 577 = 2,309 mm. The rafter factor turns a run into a rafter length (or a flat plan area into the area of roof slope): 4 m × 1.155 = 4.62 m of rafter, before any overhang.
For your own rise and run, or the roof height for a chosen pitch, use the roof pitch calculator.
How it's worked out (rise ÷ run is the same in any unit):
- Degrees = tan⁻¹(rise ÷ run); from degrees, rise ÷ run = tan(pitch)
- Rise in 12 = rise ÷ run × 12, rounded to 0.1
- Slope % = rise ÷ run × 100
- Rise per metre of run = rise ÷ run × 1,000 mm. The rise in 12 is also the rise in inches per foot of run
- Rafter factor = √(rise² + run²) ÷ run, which is 1 ÷ cos(pitch). Multiply the run by it for the rafter length to the ridge centre line, or a flat plan area by it for the area of roof slope (for tiles or felt). Add any overhang and allow for the ridge board on top.
Last checked 31 October 2026 · Last rev. 31 October 2026 · 9ce7