Roof Pitch Calculator
Find a roof’s pitch, angle, percent slope and area multiplier from rise and run, or from an angle.
How to use the Roof Pitch Calculator
- Choose the i know the.
- Enter the rise and pick its unit.
- Enter the run and pick its unit.
- Enter the roof angle and pick its unit.
- Press Calculate. The result updates automatically as you type, and you can switch the result unit at any time.
About the Roof Pitch Calculator
In the US, roof pitch is expressed as inches of rise per 12 inches of horizontal run, so a 6/12 roof climbs 6 inches for every foot. Pitch determines which roofing materials are allowed: standard asphalt shingles need at least 2/12 with double underlayment, and 4/12 or steeper for normal installation; flatter roofs need membranes such as TPO, EPDM or modified bitumen.
Pitch also affects how walkable a roof is (anything over about 7/12 typically calls for roof jacks or harnesses) and how much material is needed, through the pitch multiplier.
Formula
Pitch = 12 × Rise ÷ Run (written as x/12)
Angle = arctan(Rise ÷ Run)
Slope % = Rise ÷ Run × 100
Pitch multiplier = √(1 + (Rise ÷ Run)²)
The multiplier converts a flat (plan) area or horizontal run into the actual sloped length or area.
Example calculation
Using the default values:
- I know the = Rise and run
- Rise = 6 in
- Run = 12 in
the calculator returns:
- Pitch: 6/12
- Angle: 26.57 °
- Slope (grade): 50%
- Pitch multiplier: 1.118
- Classification: Conventional slope
Frequently asked questions
What angle is a 6/12 roof pitch?
A 6/12 pitch is about 26.57 degrees, which is a 50% slope.
What angle is a 4/12 pitch?
A 4/12 pitch is about 18.43 degrees (33.3% slope).
What is a 12/12 pitch?
A 12/12 roof rises 12 inches per 12 inches of run, a 45-degree angle and 100% slope.
What is the minimum pitch for shingles?
Asphalt shingles can be used down to 2/12 with special double-layer underlayment; 4/12 and steeper is standard.
Last updated: · Category: Construction calculators