Roof Pitch Calculator
Convert rise and run, an angle, or a pitch into all four roof slope measurements instantly.
What do you know?
Units
cm
cm
degrees
/ 12
Conventional slope. Standard shingle installation.
- Pitch
- 6/12
- Angle
- 26.57°
- Slope
- 50.0%
- Rafter multiplier
- 1.118
Results link: /roof-pitch-calculator/?rise=6&run=12&u=in
How to measure roof pitch
You need a 24″ level and a tape measure. Work from a ladder at the eave or inside the attic, never on a wet or steep roof.
- Step 1
Hold the level flat with one end touching the roof. Mark 12″ from that end.
- Step 2
Measure straight down from the 12″ mark to the roof surface. That is the rise.
- Step 3
Read it as rise over 12. Enter both numbers above for the angle and multiplier.
Roof pitch chart
Highlighted: common residential pitches| Pitch | Angle | Slope | Rafter multiplier |
|---|---|---|---|
| 1/12 | 4.76° | 8.3% | 1.003 |
| 2/12 | 9.46° | 16.7% | 1.014 |
| 3/12 | 14.04° | 25.0% | 1.031 |
| 4/12 | 18.43° | 33.3% | 1.054 |
| 5/12 | 22.62° | 41.7% | 1.083 |
| 6/12 | 26.57° | 50.0% | 1.118 |
| 7/12 | 30.26° | 58.3% | 1.158 |
| 8/12 | 33.69° | 66.7% | 1.202 |
| 9/12 | 36.87° | 75.0% | 1.250 |
| 10/12 | 39.81° | 83.3% | 1.302 |
| 11/12 | 42.51° | 91.7% | 1.357 |
| 12/12 | 45.00° | 100.0% | 1.414 |
Common roof pitches
- 4/1218.43°. Ranch homes and porches. The lowest slope for standard single-layer underlayment under shingles.
- 6/1226.57°. A very common US residential pitch. Walkable with care.
- 8/1233.69°. Common on colonial and two-story homes. Roof jacks recommended for work.
- 12/1245°. Tudor and A-frame styles. Not walkable without fall protection.
Worked example
A garage roof rises 4′ 6″ over a 9′ run. Convert both to inches: 54″ rise, 108″ run.
pitch = 54 ÷ 108 × 12 = 6/12
angle = atan(54 ÷ 108) = 26.57°
slope = 54 ÷ 108 = 50.0%
multiplier = √(54² + 108²) ÷ 108 = 1.118
rafter = 108″ × 1.118 = 120.7″ (10′ 0.7″)
angle = atan(54 ÷ 108) = 26.57°
slope = 54 ÷ 108 = 50.0%
multiplier = √(54² + 108²) ÷ 108 = 1.118
rafter = 108″ × 1.118 = 120.7″ (10′ 0.7″)
Frequently asked questions
What is the most common roof pitch?
Most pitched roofs on US homes fall between 4/12 and 9/12, and 6/12 is one of the most frequently used. Pitches in this range suit standard asphalt shingle installation and can be walked on with care.
What is the minimum pitch for asphalt shingles?
The International Residential Code (Section R905.2.2) allows asphalt shingles on slopes of 2/12 or steeper. Between 2/12 and 4/12, double underlayment is required.
How do I convert roof pitch to degrees?
Divide rise by run and take the arctangent: atan(6 ÷ 12) = 26.57°. The calculator does this for you and shows the result under Angle.
What is a rafter multiplier used for?
Multiply a horizontal run by it to get the sloped length, or multiply a roof’s flat footprint area by it to get the true roof surface area. For a 6/12 pitch the multiplier is 1.118.
Can I measure pitch from inside the attic?
Yes. Hold a level horizontally against the underside of a rafter, mark 12 inches along the level, and measure straight up from that mark to the rafter. The reading is the same as on the roof surface.
Formula
pitch = (rise ÷ run) × 12
angle° = atan(rise ÷ run) × 180 ÷ π
slope % = (rise ÷ run) × 100
multiplier = √(1 + (rise ÷ run)²)
angle° = atan(rise ÷ run) × 180 ÷ π
slope % = (rise ÷ run) × 100
multiplier = √(1 + (rise ÷ run)²)
Sources
- International Code Council, International Residential Code, Section R905.2.2 (asphalt shingle slope).
- National Roofing Contractors Association, The NRCA Roofing Manual: Steep-slope Roof Systems.
- U.S. Occupational Safety and Health Administration, Fall Protection in Residential Construction.
Formulas are shown on this page, based on the cited sources, and covered by automated tests. Methodology