1
Measure the rise
Measure how far the roof rises vertically.
Free Roofing Calculator
Roof Pitch Calculator – Pitch, Angle, Slope & Roof Area
Convert roof rise and run into pitch, roof angle and slope percentage. You can also estimate roof area, roofing squares, rafter length and waste allowance for a simple gable roof.
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Roof Measurements
Enter the vertical rise and horizontal run. Results update automatically.
Optional Roof Area Estimate
Enter building dimensions to estimate the surface area of a simple symmetrical gable roof.
The roof area estimate assumes a simple symmetrical gable roof without accounting for eaves, dormers, valleys, hips or other complex roof features.
How do you calculate roof pitch?
Roof pitch compares the vertical rise of a roof with its horizontal run. In the United States, pitch is commonly expressed as inches of rise for every 12 inches of horizontal run.
How to Use the Roof Pitch Calculator
2
Measure the run
Measure the horizontal distance for the same roof section.
3
Check pitch and angle
Review the pitch ratio, roof angle and slope percentage.
4
Estimate roof area
Add building width and length to estimate roof surface area.
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Roof Pitch Formula
Roof pitch is based on rise divided by run.
Pitch per 12 = (Rise ÷ Run) × 12
Roof angle is calculated using the arctangent of rise divided by run.
Angle = arctan(Rise ÷ Run)
Roof Pitch Example
For a roof that rises 6 inches for every 12 inches of horizontal run:
Rise = 6 in
Run = 12 in
Pitch = 6:12
Roof angle ≈ 26.57°
Slope = 50%
Common Roof Pitch Angles
2:12 pitch≈ 9.46°
4:12 pitch≈ 18.43°
6:12 pitch≈ 26.57°
8:12 pitch≈ 33.69°
10:12 pitch≈ 39.81°
12:12 pitch45°
What Is a Roofing Square?
In roofing, one roofing square equals 100 square feet of roof surface. The calculator converts the estimated roof area into roofing squares after applying the waste allowance.
Why Roof Pitch Matters
Roof pitch affects drainage, roofing material choices, roof surface area, rafter length and construction details. Steeper roofs have more surface area than a flat projection of the same building footprint.
Roof Pitch Calculator FAQ
What does a 6:12 roof pitch mean?+
A 6:12 roof pitch means the roof rises 6 inches vertically for every 12 inches of horizontal run.
What angle is a 6:12 roof?+
A 6:12 roof has an angle of approximately 26.57 degrees.
How do I convert roof pitch to degrees?+
Divide rise by run and calculate the arctangent of that ratio. The calculator performs this conversion automatically.
How do I calculate roof slope percentage?+
Divide rise by run and multiply the result by 100. A 6:12 roof therefore has a 50 percent slope.
Does roof pitch affect roof area?+
Yes. A sloped roof has more surface area than the flat footprint below it. The calculator uses the slope factor to estimate that additional area.
Does this roof area include overhangs?+
No. The basic roof area estimate uses building width and length. Add overhang dimensions separately if they need to be included.
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Planning Disclaimer
This calculator provides planning estimates only. Actual roof dimensions and construction requirements can vary because of overhangs, hips, valleys, dormers, structural design and local building requirements. Confirm final measurements and structural details before ordering materials or beginning construction.