Multiply the flat footprint by the pitch multiplier to get real roof area: 4/12 is 1.0541, 5/12 is 1.0833, 6/12 is 1.1180, 8/12 is 1.2019, 10/12 is 1.3017 and 12/12 is 1.4142. A 2,000 square foot footprint at 6/12 is 2,236 square feet of roof.
This Roof Pitch Chart is the complete reference table for converting every standard roof pitch from 1/12 through 24/12 into the angle in degrees and the slope multiplier used to convert flat footprint area into actual sloped roof area. A 4/12 roof has a multiplier of 1.054, meaning the actual roof surface is 5.4% larger than the building footprint. A 12/12 roof has a multiplier of 1.414. Bookmark this chart for quick reference when sizing shingles, underlayment, and decking.
The full conversion between roof pitch, angle in degrees, slope percentage and the area multiplier used to turn a flat footprint into real roof area. These are the same figures the pitch calculator returns.
| Pitch | Angle | Slope % | Multiplier | 2,000 sq ft footprint becomes |
|---|---|---|---|---|
| 1/12 | 4.8° | 8.3% | 1.0035 | 2,007 sq ft |
| 2/12 | 9.5° | 16.7% | 1.0138 | 2,028 sq ft |
| 3/12 | 14.0° | 25.0% | 1.0308 | 2,062 sq ft |
| 4/12 | 18.4° | 33.3% | 1.0541 | 2,108 sq ft |
| 5/12 | 22.6° | 41.7% | 1.0833 | 2,167 sq ft |
| 6/12 | 26.6° | 50.0% | 1.1180 | 2,236 sq ft |
| 7/12 | 30.3° | 58.3% | 1.1577 | 2,315 sq ft |
| 8/12 | 33.7° | 66.7% | 1.2019 | 2,404 sq ft |
| 9/12 | 36.9° | 75.0% | 1.2500 | 2,500 sq ft |
| 10/12 | 39.8° | 83.3% | 1.3017 | 2,603 sq ft |
| 12/12 | 45.0° | 100.0% | 1.4142 | 2,828 sq ft |
| 14/12 | 49.4° | 116.7% | 1.5366 | 3,073 sq ft |
| 16/12 | 53.1° | 133.3% | 1.6667 | 3,333 sq ft |
| 18/12 | 56.3° | 150.0% | 1.8028 | 3,606 sq ft |
| 20/12 | 59.0° | 166.7% | 1.9437 | 3,887 sq ft |
| 24/12 | 63.4° | 200.0% | 2.2361 | 4,472 sq ft |
Each of these answers the same four questions for one specific pitch: the angle in degrees, the slope percentage, the area multiplier, and what it means for material and for walking on the roof.
0.5/12 · 1/12 · 1.5/12 · 2/12 · 2.5/12 · 3/12 · 3.5/12 · 4/12 · 4.5/12 · 5/12 · 5.5/12 · 6/12 · 6.5/12 · 7/12 · 7.5/12 · 8/12 · 8.5/12 · 9/12 · 9.5/12 · 10/12 · 10.5/12 · 11/12 · 11.5/12 · 12/12 · 13/12 · 14/12 · 15/12 · 16/12 · 17/12 · 18/12 · 20/12 · 21/12 · 22/12 · 24/12
The chart runs in both directions. If you know the pitch, read across for the angle, the slope percentage and the multiplier. If you have an angle from a phone level or a survey, find the closest row and read back to the pitch — but round to the nearest standard pitch rather than trying to order material against 27.1 degrees, because rafters and trusses are cut to whole pitches.
Under 2/12 you are on a low-slope roof and asphalt shingles are out — the code will not allow them and no manufacturer will warrant them. Between 2/12 and 4/12 shingles are allowed with a doubled underlayment layer. From 4/12 to 9/12 is the ordinary residential band: walkable with sensible footwear, standard installation details, standard labour rates. From 9/12 up, add roof jacks, staging and time. Above 12/12 you are into specialist territory, and material waste climbs because every course has to be cut to a steeper rake.
Take the arctangent of rise divided by run. A 4/12 pitch is arctan(4/12) = 18.43 degrees; 6/12 is 26.57 degrees; 12/12 is exactly 45 degrees.
A 12/12 pitch rises 12 inches for every 12 inches of run — a 45 degree angle and a 100% slope. Its area multiplier is 1.4142, so it needs about 41% more material than the footprint suggests.
It converts the flat footprint area into actual roof surface area. Multiply the ground area the roof covers by the multiplier for your pitch to get the area you must buy material for.
Up to about 6/12 most people can walk with proper footwear. From 7/12 to 9/12 you want roof jacks. Above 9/12 staging or a harness is the sensible minimum.