Formula
How this estimate works
pitch = rise / run x 12; angle = arctan(rise / run)
A roof with 6 in rise over 12 in run is a 6:12 pitch, about 26.57 degrees, with a 1.118 pitch multiplier.
How roof pitch is calculated
Roof pitch in the United States is usually expressed as inches of rise for every 12 inches of run. Divide rise by run, then multiply by 12. The same ratio can be converted to degrees with arctangent.
Why pitch multiplier matters
A roof's surface area is larger than its flat footprint. The pitch multiplier estimates the extra surface area caused by slope and is useful when estimating roofing materials.
Assumptions used
- Pitch is shown as inches of rise per 12 inches of horizontal run.
- Rafter length uses the same units entered for rise and run.
- Pitch multiplier estimates sloped surface area from flat footprint area.
Before you order materials
- Measure horizontal run, not the sloped rafter distance.
- Use the multiplier with actual roof footprint measurements.
- Check roofing manufacturer requirements for low-slope roofs.
Frequently asked questions
What does 6:12 pitch mean?
It means the roof rises 6 inches for every 12 inches of horizontal run.
Is pitch the same as degrees?
No. Pitch is a rise-over-run ratio, while degrees describe the angle. This calculator shows both.
Can I use this for material estimates?
Use the pitch multiplier as a planning estimate, then confirm roof measurements before ordering materials.