Roof pitch calculator
From a quick measurement to a clear answer. Find your roof’s pitch, angle, and slope in seconds.
Enter any measurement
Edit rise/run, degrees, or percent. All three stay in sync.
Area viewed from above, for roof planes sharing this pitch.
Roof pitch
conventional4:12
Angle
18.4°
Slope
33.33%
Standard pitch: inches of rise per 12 inches of run.
Area multiplier 1.054×
How to use this calculator
- Enter the vertical rise and horizontal run in inches, or enter an angle or slope percentage. The other fields update as you type.
- The result always uses a 12-inch run. For example, 8 inches of rise over 24 inches of run becomes 4:12, 18.4°, and 33.33%.
- Optionally enter the roof’s horizontal projected area in square feet. Surface area = projected area ÷ cos(angle). For mixed pitches, calculate each section separately. This excludes waste and material allowance.
Angles must be at least 0° and less than 90°. A 90° surface is vertical and has no finite x:12 roof pitch. Measurements are calculated at full precision; displayed results are rounded.
About the slope labels
This calculator uses asphalt-shingle application bands: flat (including very low slope) below 2:12; low slope from 2:12 to below 4:12; conventional from 4:12 through 21:12; steep slope above 21:12. These descriptive labels are not a roof-access safety classification.
“Flat” below 2:12 is this tool’s grouping. Follow the roofing manufacturer’s instructions for material suitability and installation.
Sources: ARMA Residential Asphalt Roofing Manual, page 17 and ARMA steep-slope guidance.
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A quick reference for pitch, degrees, and slope.
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Get to know rise, run, and the measurements you need.
Read the guideStandard Roof Pitch
An introduction to common roof pitches in the U.S.
Read the guideA few helpful answers
Roof pitch, explained
What does a 6/12 roof pitch mean?
A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal run. Its angle is approximately 26.6 degrees.
Is run the same as the full width of a roof?
No. Run is the horizontal distance for the slope you are measuring, not the distance along the roof. For a simple, symmetrical gable roof, one side’s run is half the total span.
How do I know my roof pitch?
Check a roof measurement report, or measure from a safely accessible attic. Hold a level horizontally under a rafter and measure its vertical rise over 12 inches of run. A 4-inch rise means a 4/12 pitch. For a different run, divide rise by run and multiply by 12.
What is the most common roof pitch?
Most U.S. residential roof slopes fall between 4/12 and 9/12, according to GAF. The pitch of an individual home varies with its design, so measure your own roof rather than assuming a typical pitch.
What is a 4/12 roof pitch in degrees?
A 4/12 roof pitch is approximately 18.4 degrees, calculated as arctan(4 ÷ 12). It rises 4 inches for every 12 inches of horizontal run and has a slope of about 33.33%.