Roof measurement
Roof pitch and slope converter
Determine roof pitch and slope. Homeowner measures rise/run or knows an angle.
Calculate the slope
Adjustable example. Change these illustrative inputs to match your task, then recalculate. Reset restores the example and its result.
Use rise and run, or clear both before entering an angle. The two input paths are alternatives.
Understand the result
How this calculation works
Roof pitch expresses rise for every 12 inches of horizontal run.
Steps
- Enter rise and run with their units, or clear both fields before using the angle alternative.
- Submit once the two measurements describe the same roof section.
The form starts with 6 in rise and 12 in run. Reset restores that example. The angle placeholder is not an entered angle.
Formula
slope = rise ÷ run; pitch = 12 × slope; angle in degrees = atan(slope) × 180 ÷ π; rafter multiplier = √(1 + slope²).
Variables and units
Rise and run: positive finite values in in, ft, cm or m, selected separately. The alternative angle must be greater than 0 and less than 90 degrees. Pitch is normalized to 12 inches of run; slope and multiplier are unitless.
What the result means
The result describes the measured right triangle. It does not identify the pitch of other roof sections automatically.
Worked example
Inputs: Rise = 6; Run = 12; Rise Unit = in; Run Unit = in.
Calculation: 6 in rise, 12 in run → slope 0.5 (50%); pitch 6:12; angle 26.57°; multiplier 1.1180.
Result: 6.00:12.
Use an angle instead of rise and run
Inputs: Rise = not entered; Run = not entered; Angle = 45.
Calculation: Clear rise and run, then enter 45 degrees. tan(45°) = 1, so the pitch is 12:12 and the multiplier is √2.
Result: 12.00:12.
Mix rise and run units
Inputs: Rise = 0.5; Run = 30.48; Rise Unit = ft; Run Unit = cm.
Calculation: A 0.5 ft rise equals 6 in; a 30.48 cm run equals 12 in. The ratio remains 0.5, giving a 6:12 pitch.
Result: 6.00:12.
Frequently asked questions
Can I use an angle instead?
Yes, but clear rise and run first so the form does not receive conflicting paths.
Do units have to match?
No. The calculator converts each entry before comparing the ratio.
Does pitch tell me the roof area?
No. It gives the slope relationship; area needs its own measurements.