Measurement basis
Roof pitch compares vertical rise with horizontal run, while an angle uses degrees and a rafter length follows the slope. This calculator translates a safely obtained rise-and-run measurement into all three forms. It also reports the multiplier that converts a horizontal roof projection into sloped surface area when pitch is uniform. The slope length represents a straight geometric line between the two measurement points. It excludes overhangs, ridge deductions, birdsmouth cuts and framing allowances, so it should not be treated as a ready-to-cut rafter schedule.
Geometry, units and worked example
A worked example
A rise of 6 ft over a 12 ft horizontal run is 6/12 pitch, 26.57°, 50% slope, a 1.1180 area multiplier and 13.42 ft geometric slope length.
Enter consistent dimensions
- Use rise and horizontal run measured in the same units.
- Read pitch as rise per 12 inches of horizontal distance.
- Use the multiplier only for roof areas sharing that pitch.
Where the model stops
- A zero rise is a flat geometric plane, not a drainage recommendation.
- Do not climb onto a roof merely to obtain dimensions for this calculator.
- A framing member’s cut length includes project-specific geometry beyond this right triangle.
Frequently asked questions
Is 6/12 pitch the same as 50 percent slope?
Yes. Six units of rise over twelve horizontal units is a 0.5 ratio, or 50%.
Is 6/12 pitch a 45 degree roof?
No. Its angle is about 26.57 degrees. A 12/12 pitch is 45 degrees.
Can slope distance be entered as run?
No. Run must be horizontal; slope distance is longer on a pitched roof.
Read the project guides
- From Roof Footprint to Shingle Bundles: A Checked Takeoff
Convert a simple roof footprint and pitch into sloped area, then calculate field shingles, starter and ridge caps with product-specific coverage.
Calculation method: JICWH methodology. Examples are planning assumptions, not product recommendations.