Roof Pitch Calculator
Pitch as an angle, as a multiplier, and as rafter length.
Pitch 6/12
26.6°
- Pitch multiplier
- 1.1180
- Angle from horizontal
- 26.57°
- Grade
- 50.0%
- Footprint
- 2,000 sq ft
- Actual roof area
- 2,236 sq ft
- Extra area from slope
- 236 sq ft
- Rafter length (half span)
- 16.77 ft
- Ridge height above wall
- 7.50 ft
Rafter length is the sloped run from wall to ridge, before any overhang or plumb cut.
Now price the roof → roof replacement cost calculator
How this is calculated
multiplier = √(rise² + run²) ÷ run angle = arctan(rise ÷ run) roof area = footprint × multiplier rafter = (span ÷ 2) × multiplier
The multiplier is nothing but the hypotenuse of the rise-over-run triangle. That is why a 12/12 roof comes out at exactly √2, or 1.4142 — the rise equals the run, so the slope is the diagonal of a square.
Roof pitch chart
Every row derives from the same two functions as the calculator above — nothing here is typed in.
| Pitch | Angle | Multiplier | Grade | Roof area per 1,000 sq ft |
|---|---|---|---|---|
| 1/12 | 4.76° | 1.0035 | 8.3% | 1,003 sq ft |
| 2/12 | 9.46° | 1.0138 | 16.7% | 1,014 sq ft |
| 3/12 | 14.04° | 1.0308 | 25.0% | 1,031 sq ft |
| 4/12 | 18.43° | 1.0541 | 33.3% | 1,054 sq ft |
| 5/12 | 22.62° | 1.0833 | 41.7% | 1,083 sq ft |
| 6/12 | 26.57° | 1.1180 | 50.0% | 1,118 sq ft |
| 7/12 | 30.26° | 1.1577 | 58.3% | 1,158 sq ft |
| 8/12 | 33.69° | 1.2019 | 66.7% | 1,202 sq ft |
| 9/12 | 36.87° | 1.2500 | 75.0% | 1,250 sq ft |
| 10/12 | 39.81° | 1.3017 | 83.3% | 1,302 sq ft |
| 11/12 | 42.51° | 1.3566 | 91.7% | 1,357 sq ft |
| 12/12 | 45.00° | 1.4142 | 100.0% | 1,414 sq ft |
What each range means in practice
| Range | Called | What changes |
|---|---|---|
| Under 2/12 | Low slope | Asphalt shingles not rated; needs a membrane |
| 2/12 to 4/12 | Low | Walkable, ice-and-water shield usually required |
| 4/12 to 6/12 | Conventional | The most common residential range |
| 6/12 to 9/12 | Steep | Roof jacks and staging; labor rises |
| Over 9/12 | Very steep | Harnesses, slower work, highest labor per square |
Frequently asked questions
What is roof pitch?
Pitch is how many inches a roof rises for every 12 inches it runs horizontally. A 6/12 roof climbs 6 inches per foot of run. It is written as a ratio rather than an angle because rafters are cut and framing is laid out in inches of rise, not in degrees.
How do I measure my roof pitch?
Hold a level against a rafter or against the roof surface, mark 12 inches along it, then measure straight down from that mark to the roof. That vertical distance in inches is the rise. From inside the attic against a rafter is safer than on the roof and gives the same answer.
What is the pitch multiplier for?
It converts the footprint a roof covers into the actual sloped surface you have to buy material for. A 6/12 roof is 1.118 times its footprint, so a 2,000 square foot footprint is 2,236 square feet of roof. Ordering shingles off the footprint is the classic way to come up short.
What is considered a steep roof?
Anything above 6/12 is generally called steep, and above 8/12 usually requires roof jacks, harnesses or staging, which raises labor cost noticeably. Below 2/12 is called low slope, and most asphalt shingles are not rated for it — those roofs need a membrane instead.
How do I convert pitch to degrees?
The angle is the arctangent of rise divided by run. A 6/12 pitch works out to 26.57 degrees and a 12/12 is exactly 45 degrees, because the rise equals the run. Degrees are useful for solar panel layout and for cutting with a miter saw, but framing is still specified as a ratio.
Does pitch change how much a roof costs?
Twice over. A steeper roof has more surface area for the same house, so more material, and it is slower and riskier to work on, so higher labor per square. That is why quotes on identical footprints can differ substantially between a ranch and a steep gable.
Geometry is exact; the practical notes are general guidance. Shingle manufacturers set their own minimum slope, and local code governs ice barrier requirements — check both before ordering material for a low-slope roof.