Free tool
Roof Pitch Calculator
Find your roof pitch from rise and run, or convert an angle to pitch. The calculator gives you the pitch in x/12, the angle in degrees, the slope percentage and the roof area multiplier, and shows which roofing materials your pitch allows.
- Pitch, angle & slope %
- Roof area multiplier
- Rafter length
- Material minimum slopes
18.4° roof. Here is how the minimum slopes in the International Residential Code line up with your pitch.
Get a free roof measurementPrice a new roofRoofing materials at this pitch
Minimum slopes from the 2021 International Residential Code (R905). Arizona cities adopt the code with local amendments, so check with your building department.
Roof pitch chart
Common pitches with their angle, slope and area multiplier.
| Pitch | Angle | Slope | Multiplier | Type |
|---|---|---|---|---|
| 1/12 | 4.8° | 8.3% | 1.003 | Flat / low slope |
| 2/12 | 9.5° | 16.7% | 1.014 | Low pitch |
| 2½/12 | 11.8° | 20.8% | 1.021 | Low pitch |
| 3/12 | 14.0° | 25.0% | 1.031 | Low pitch |
| 4/12 | 18.4° | 33.3% | 1.054 | Low pitch |
| 5/12 | 22.6° | 41.7% | 1.083 | Moderate pitch |
| 6/12 | 26.6° | 50.0% | 1.118 | Moderate pitch |
| 7/12 | 30.3° | 58.3% | 1.158 | Moderate pitch |
| 8/12 | 33.7° | 66.7% | 1.202 | Moderate pitch |
| 9/12 | 36.9° | 75.0% | 1.250 | Steep pitch |
| 10/12 | 39.8° | 83.3% | 1.302 | Steep pitch |
| 12/12 | 45.0° | 100.0% | 1.414 | Steep pitch |
Your exact price
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Not keen on climbing a ladder? A free roof inspection includes measurements, pitch and photos of your roof’s condition, plus a written estimate if you need work.
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How to measure
How to Find Your Roof Pitch
Roof pitch is the rise of a roof over 12 inches of horizontal run, written as rise/12. You can measure it three ways:
1. From the attic
Hold a level against the bottom of a rafter, mark 12 inches along the level, then measure straight up from the mark to the rafter. This is the safest method.
2. From a ladder at the eave
Rest a level on the roof surface with one end touching it, hold it level, and measure from the 12-inch mark down to the roof. Do not walk on tile; it cracks easily.
3. With a phone or a known angle
Many phone level apps read the angle in degrees. Switch the calculator to “Angle” to convert it to pitch.
From pitch to roof area
Multiply your footprint, including overhangs, by the pitch multiplier to get roof area. Our roof square footage calculator does it for the whole house and adds squares and shingle bundles.
Arizona roofs
Pitch and Roofing Material in Arizona
Arizona has plenty of both: low- to moderate-pitch tile and shingle roofs, and flat roofs behind parapet walls. Your pitch narrows the choice of material.
Tile roofs
Concrete and clay tile need at least 2½/12, with double underlayment below 4/12.
Tile roofing →▤Shingle roofs
Asphalt shingles need at least 2/12, with double underlayment below 4/12.
Shingle roofing →▭Flat & low-slope roofs
Below 2/12, use a low-slope system: spray foam, TPO or modified bitumen, at 1/4:12 minimum.
Foam roofing →≡Metal roofs
Standing seam can go as low as 1/4:12. Lapped panels without sealant need 3/12.
Metal roofing →Reviews
What Arizona Homeowners Say
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Each tool uses the same Arizona market data, so the numbers line up from one calculator to the next.
Roof Replacement Cost Calculator
Price a new roof by size, material, pitch and add-ons, with every roof type side by side.
Replacement calculator →+Roof Repair Cost Calculator
Leaks, broken tile, flashing, pipe boots, flat-roof patches and emergency tarps.
Repair calculator →▭Flat Roof & Coating Cost Calculator
Spray foam, foam recoats, silicone and acrylic coatings, TPO and modified bitumen, plus gallons.
Flat roof calculator →ft²Roof Square Footage Calculator
Turn your home’s footprint and pitch into roof square feet, squares and shingle bundles.
Square footage calculator →FAQ
Roof Pitch Questions
How do I calculate roof pitch?
Hold a level horizontally against the roof or a rafter, mark 12 inches along it, and measure straight up from that mark to the roof surface. That vertical distance is the rise. A 4-inch rise over 12 inches of run is a 4/12 pitch.
What is a 4/12 roof pitch in degrees?
A 4/12 pitch is about 18.4 degrees, a 33.3% slope. Its roof area multiplier is about 1.054, so the roof surface is roughly 5.4% larger than the flat area it covers.
What is a roof pitch multiplier?
It is the factor that turns flat footprint area into actual roof surface area: the square root of 1 plus (rise ÷ 12) squared. A 6/12 roof has a multiplier of about 1.118, so a 2,000 sq ft footprint has about 2,236 sq ft of roof.
What is the minimum pitch for a tile roof?
Under the International Residential Code, clay and concrete tile need a slope of at least 2½/12. Between 2½/12 and 4/12, the code calls for a double layer of underlayment.
What is the minimum pitch for asphalt shingles?
Asphalt shingles need a slope of at least 2/12. Between 2/12 and 4/12, the code requires double underlayment. Below 2/12, use a low-slope system such as spray foam, TPO or modified bitumen.
Does roof pitch change the cost of a new roof?
Yes, in two ways. A steeper roof has more surface area to cover, and steep roofs need more safety equipment and labor time. Moderate pitches typically add about 5–15% to a replacement, and steep roofs about 20–35%. Price yours with the roof replacement cost calculator.
Need a Roof Measured or Priced?
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