Construction Calculator - Roofing

Roof Pitch Calculator

Convert rise and run into roof pitch, angle, and slope factor.

Reviewed: August 26, 2026

Calculate Roof Pitch

For the Roof Pitch Calculator, enter rise and run. It converts rise and run into pitch ratio, angle, and slope factor; it does not calculate roof area or material quantity.

Construction measuring tools arranged beside a residential building project

Formula used

Slope ratio = rise ÷ run; angle = arctan(rise ÷ run); slope factor = √[1 + (rise ÷ run)²]

Roof pitch triangle showing vertical rise, horizontal run, rafter length, and pitch angle.

Worked roof pitch example

Roof Pitch Calculator example: 6.6 in ÷ 8.34 in = 0.7914. The angle is arctan(0.7914) = 38.36°, and the slope factor is √(1 + 0.7914²) = 1.275.

What the converted result represents

Use the angle and slope factor to coordinate layout and area estimates, keeping the rise-over-run ratio visible for trade communication.

Limits of the geometric model

Measurements taken from finished surfaces, sagged framing, unequal roof planes, and confusing rafter length with horizontal run can skew the ratio.

Questions specific to this calculation

What is the difference between roof pitch and slope factor?

Enter vertical rise and horizontal run in the same unit. For conventional pitch notation, run is often entered as 12 inches, but the math accepts any compatible pair.