Roof Pitch Calculator: Pitch, Angle & Slope

Enter the rise and run of your roof, or the angle, and get the pitch in x/12, the angle in degrees, the slope as a percent and the pitch factor.

Rise

Run

Roof angle

degrees

–roof pitch

–angle

–slope as a percent

–pitch factor

–rise : run

Measure the rise over a level 12 inch run with a level and tape, from the roof surface or the underside of a rafter.

What roof pitch means

Roof pitch is how many inches the roof rises for every 12 inches it runs level. A 6/12 roof rises 6 inches over 12 inches of run. The same slope can be written as an angle (26.6 degrees for 6/12) or as a percent (50 percent).

How to measure roof pitch

On the roof: hold a level flat against the roof, mark 12 inches along it, and measure straight down from that mark to the roof surface. That’s the rise.
In the attic: do the same against the underside of a rafter.
From the gable end: measure the height of the gable and half the building width, then enter those as rise and run.
With a phone: many level apps show the angle. Enter it under “Angle”.

Roof pitch formulas

Pitch = rise ÷ run × 12
Angle = arctangent of (rise ÷ run)
Slope percent = rise ÷ run × 100
Pitch factor = √(1 + (rise ÷ run)²), used to turn a flat area into roof area

Roof pitch chart

Pitch	Angle	Slope
2/12	9.5°	16.7%
3/12	14.0°	25.0%
4/12	18.4°	33.3%
5/12	22.6°	41.7%
6/12	26.6°	50.0%
7/12	30.3°	58.3%
8/12	33.7°	66.7%
9/12	36.9°	75.0%
10/12	39.8°	83.3%
12/12	45.0°	100%

Pitch and roofing materials

Below 2/12: treated as a low-slope or flat roof, usually covered with a membrane such as TPO or EPDM.
2/12 to 4/12: asphalt shingles are allowed under common US codes, but with extra underlayment.
4/12 and steeper: standard shingle installation.
Metal: minimum pitch depends on the panel system, so check the maker’s instructions.