Roof pitch calculator
Type the rise over a run, or the roof angle, and this calculator gives the pitch over 12, the angle in degrees, the pitch multiplier and the grade. Add the level run to get the rafter length and ridge height. Below it is a roof pitch chart from 1/12 to 24/12. Free, no account.
Rise and run
Hold a level flat against the roof or rafter, measure 12 inches along it, then measure straight down to the roof. That drop is the rise. Any run works if you use the same units for both.
Rafter length
On a gable roof the run is half the building's width, wall to the center of the ridge.
Level distance past the wall
Conventional: 4/12 to 8/12
The usual range for shingle roofs. Most crews can walk it with standard safety gear.
- Rafter, wall to ridge: 14 ft × 1.118
- 15 ft 7.75 in
- With the 12 in overhang
- 16 ft 9.25 in
- Ridge height above the wall
- 7 ft
Worked out in your browser from the numbers you type. Nothing is looked up or saved. No prices are shown here. Confirm every number on site.
How to calculate roof pitch
Roof pitch is the rise in inches for every 12 inches of level run. You can measure it on the roof, in the attic or from a gable end.
- Hold a level against the roof surface or under a rafter, perfectly level.
- Mark 12 inches along the level from where it touches.
- Measure straight down (or up) from that mark to the roof or rafter. That's the rise.
- Write it as rise over 12. A 6 inch rise is a 6/12 pitch.
- For the angle, take the arctangent of the rise divided by 12. For the multiplier, take the square root of 1 plus that ratio squared.
ExampleA 6/12 roof, 28 ft wide
- Rise 6 in over 12 in of run
- 6/12
- Angle: arctan(6 ÷ 12)
- 26.57°
- Multiplier: √(1 + 0.5²)
- 1.118
- Rafter: 14 ft run × 1.118
- 15 ft 7.75 in
- With a 12 in overhang
- 16 ft 9.25 in
- Ridge height above the walls
- 7 ft
Rafter length here is along the top of the rafter. Allow for the ridge board and the plumb cut when you cut it.
Roof pitch chart
Every pitch from 1/12 to 24/12 with its angle, pitch multiplier and grade. The shaded rows, 4/12 to 8/12, cover most shingle roofs.
| Pitch | Angle | Multiplier | Grade |
|---|---|---|---|
| 1/12 | 4.76° | 1.003 | 8.3% |
| 2/12 | 9.46° | 1.014 | 16.7% |
| 3/12 | 14.04° | 1.031 | 25.0% |
| 4/12 | 18.43° | 1.054 | 33.3% |
| 5/12 | 22.62° | 1.083 | 41.7% |
| 6/12 | 26.57° | 1.118 | 50.0% |
| 7/12 | 30.26° | 1.158 | 58.3% |
| 8/12 | 33.69° | 1.202 | 66.7% |
| 9/12 | 36.87° | 1.250 | 75.0% |
| 10/12 | 39.81° | 1.302 | 83.3% |
| 11/12 | 42.51° | 1.357 | 91.7% |
| 12/12 | 45.00° | 1.414 | 100.0% |
| Pitch | Angle | Multiplier | Grade |
|---|---|---|---|
| 13/12 | 47.29° | 1.474 | 108.3% |
| 14/12 | 49.40° | 1.537 | 116.7% |
| 15/12 | 51.34° | 1.601 | 125.0% |
| 16/12 | 53.13° | 1.667 | 133.3% |
| 17/12 | 54.78° | 1.734 | 141.7% |
| 18/12 | 56.31° | 1.803 | 150.0% |
| 19/12 | 57.72° | 1.873 | 158.3% |
| 20/12 | 59.04° | 1.944 | 166.7% |
| 21/12 | 60.26° | 2.016 | 175.0% |
| 22/12 | 61.39° | 2.088 | 183.3% |
| 23/12 | 62.45° | 2.162 | 191.7% |
| 24/12 | 63.43° | 2.236 | 200.0% |
Pitch multiplier: from footprint to roof area
A roof covers more area than the ground under it. Multiply the footprint by the pitch multiplier to get the sloped area roofers price, then divide by 100 for squares.
Use the same multiplier for lengths: a rafter, a rake edge or a valley run measured on a plan gets longer by the multiplier once it's on the slope. For a roof with sections at different pitches, the roof square footage calculator adds them up for you.
ExampleA 42 × 32 ft roof at 6/12
- Footprint, eave to eave: 42 × 32
- 1,344 sq ft
- × 1.118 pitch multiplier
- 1,503 sq ft
- 1,503 ÷ 100
- 15.0 squares
Measured on the slope, so no second multiplier belongs on top of it.
What the pitch changes on a roofing job
Pitch decides what can go on the roof, how the crew works it and how much material it takes.
By pitch range
- Low slope: under 2/12. Too flat for asphalt shingles. Price a membrane or another low-slope system.
- Low pitch: 2/12 to under 4/12. Shingles are allowed, with two layers of underlayment under the code (IRC R905.2.2).
- Conventional: 4/12 to 8/12. The usual range for shingle roofs.
- Steep: over 8/12. Steeper than 33.7°. Plan for roof jacks, harness time and a slower crew.
In a Measured Bid estimate
- Roof area comes from each plane's sloped area, so there's no multiplier to apply.
- Planes under 2/12 are flagged as low slope and priced at a separate rate when you set one.
- Planes over 8/12 get your steep-roof adjustment, on those squares only.
- Waste is set by roof type: gable, hip, complex, shed or low slope.
Get the pitch of every plane from an address
You don't need a ladder to find the pitch. Measured Bid's free roof measurement tool looks the house up in Google's aerial roof data and lists every roof plane with its direction, pitch and sloped area.
On our model house that's 4 planes, the steepest at 5/12, and 2,344 sq ft of roof. Confirm the pitch on site before you order.
Planes
- North, 5/12962 sq ft
- South, 5/12962 sq ft
- East, 5/12210 sq ft
- West, 5/12210 sq ft
Turn the pitch into a roof price
In Measured Bid you set a price per square for each material, tear-off per layer, waste by roof type, a steep-roof adjustment and a job minimum. Then any address becomes an estimate.
FAQ
How do you calculate roof pitch?
Measure how many inches the roof rises over 12 inches of level run. That number over 12 is the pitch, so a roof that rises 6 inches in 12 is a 6/12 pitch. If you measured over a different run, divide the rise by the run and multiply by 12.
How do I convert roof pitch to degrees?
Take the arctangent of the rise divided by 12. A 4/12 roof is 18.4 degrees, a 6/12 roof is 26.6 and a 12/12 roof is 45.0. The chart on this page lists every pitch from 1/12 to 24/12.
What is a roof pitch multiplier?
It turns a level length or area into the sloped one: the square root of 1 plus (rise ÷ 12) squared. A 6/12 roof's multiplier is 1.118, so 1,344 sq ft of footprint is about 1,503 sq ft of roof.
What pitch is too low for shingles?
The International Residential Code (section R905.2.2) allows asphalt shingles down to 2/12, with two layers of underlayment from 2/12 up to 4/12. A roof under 2/12 needs a low-slope system such as a membrane. Check your local code, which can be stricter.
How do I find rafter length?
Multiply the level run by the pitch multiplier. On a gable roof the run is half the building's width. Add the overhang the same way: its level length times the multiplier.
Can I find the pitch without getting on the roof?
Yes. Measured Bid's free roof measurement tool reads the pitch of every roof plane from aerial data for the address. From the ground, you can hold a level and a tape against the rake at a gable end.
Related pages and tools
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