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How to use the roof pitch calculator
- Rise & run: enter how far the roof goes up (rise) over a horizontal distance (run), in any one unit. A rise of 4 ft over a run of 8 ft is a 6/12 pitch.
- Angle: enter degrees from a digital level, angle finder or your plans.
- From a photo: stand back from a gable end, hold the phone level and take the photo square-on. Tap both ends of the sloped roof edge. For a better reading, tap two points on something level, like the gutter, so the tool can cancel out camera tilt. The photo never leaves your device.
- Phone level: on a phone, lay it flat on a rafter or a straightedge set along the slope and tap Hold.
Every result goes into the page address, so you can copy the link or print the result for your roofer.
Roof pitch, degrees and multiplier table
| Pitch | Degrees | Multiplier | Hip / valley factor | Grade |
|---|---|---|---|---|
| 1/12 | 4.76° | 1.003 | 1.417 | 8.3% |
| 2/12 | 9.46° | 1.014 | 1.424 | 16.7% |
| 3/12 | 14.04° | 1.031 | 1.436 | 25.0% |
| 4/12 | 18.43° | 1.054 | 1.453 | 33.3% |
| 5/12 | 22.62° | 1.083 | 1.474 | 41.7% |
| 6/12 | 26.57° | 1.118 | 1.500 | 50.0% |
| 7/12 | 30.26° | 1.158 | 1.530 | 58.3% |
| 8/12 | 33.69° | 1.202 | 1.563 | 66.7% |
| 9/12 | 36.87° | 1.250 | 1.601 | 75.0% |
| 10/12 | 39.81° | 1.302 | 1.641 | 83.3% |
| 11/12 | 42.51° | 1.357 | 1.685 | 91.7% |
| 12/12 | 45.00° | 1.414 | 1.732 | 100.0% |
| 14/12 | 49.40° | 1.537 | 1.833 | 116.7% |
| 16/12 | 53.13° | 1.667 | 1.944 | 133.3% |
| 18/12 | 56.31° | 1.803 | 2.062 | 150.0% |
| 24/12 | 63.43° | 2.236 | 2.449 | 200.0% |
The formulas
- Pitch = rise ÷ run × 12, written as x/12.
- Angle = atan(rise ÷ 12). A 12/12 roof is exactly 45°.
- Pitch multiplier (rafter or slope factor) = √(1 + (rise ÷ 12)²). Multiply a footprint area by it to get the roof area, which is what the roofing squares calculator does.
- Hip and valley factor = √(2 + (rise ÷ 12)²), for two planes of the same pitch meeting at a right angle in plan.
Is your roof walkable?
OSHA's construction rules (29 CFR 1926.500) call a roof of 4 in 12 or less "low-slope" and anything steeper a "steep roof", which changes the fall protection required. Beyond that line there is no official walkability rating. The bands this calculator shows are common trade practice: up to about 6/12 most roofers walk a dry roof; from about 7/12 they set roof jacks; from 10/12 the work is done from staging. Wet, frosty or dusty surfaces change everything, and none of this replaces fall protection.
Pitch and roofing materials
Each covering has a minimum slope in the 2024 International Residential Code, chapter 9: ¼/12 for membranes and standing-seam metal, 2/12 for asphalt shingles (with double underlayment below 4/12), 2½/12 for clay and concrete tile, 3/12 for wood shakes and metal shingles and 4/12 for slate. Expand Which roofing materials are allowed under the result to check yours. To compare what those materials cost on your roof, use the roof cost calculator.
Questions people ask
What does a 6/12 roof pitch mean?
The roof rises 6 inches for every 12 inches it runs horizontally. That is an angle of 26.57 degrees and a pitch multiplier of 1.118, so the roof surface is about 11.8% larger than the area it covers.
How do I convert roof pitch to degrees?
Divide the rise by 12, take the arctangent, and convert to degrees: angle = atan(rise ÷ 12). For a 4/12 pitch that is atan(0.333) = 18.43°. Going the other way, rise = 12 × tan(angle).
What is a pitch multiplier?
It is the number you multiply a footprint (plan) area by to get the sloped roof area: √(1 + (rise ÷ 12)²). A 6/12 roof has a multiplier of 1.118 and a 12/12 roof has 1.414. The same number turns a horizontal run into a rafter length.
How can I measure roof pitch without going on the roof?
Three ways, all here. Photograph a gable end straight on and tap along the roof edge. Lay your phone on a rafter in the attic and use its tilt sensor. Or in the attic, hold a level horizontally against a rafter, measure 12 inches along the level, then measure straight up to the underside of the rafter: that number is the rise.
What is the most common roof pitch?
Most homes fall between 4/12 and 9/12, the range builders call conventional slope. Below 4/12 is low-slope (OSHA draws that line at 4 in 12), and above 9/12 is steep enough that roofers need roof jacks or staging.
What is the lowest pitch for asphalt shingles?
The International Residential Code allows asphalt shingles down to 2/12, but from 2/12 up to 4/12 they need two layers of underlayment (IRC R905.2.2). Below 2/12, use a low-slope membrane or a metal system rated for it.
Is a 7/12 roof walkable?
Many roofers walk a dry 7/12 roof in soft-soled shoes, but it is at the edge. From about 7/12 or 8/12 up, most crews use roof jacks and fall protection, and many price a steep-roof charge. If you are not a roofer, do not walk any roof you are unsure of.
What is the hip and valley factor?
Where two roof planes of the same pitch meet at a right angle in plan, the hip or valley is longer than the plan run of a common rafter by √(2 + (rise ÷ 12)²). At 6/12 that factor is 1.5, so a hip over a 16 ft run is 24 ft long.