What is roof pitch and what is a pitch factor?
Roof pitch is how many inches a roof rises for every 12 in of horizontal run, written as rise/12, so 6/12 rises 6 in per foot. The pitch factor is the multiplier that turns flat plan area into the true sloped surface area you order materials for.
Formula
Pitch factor = square root of (1 + (rise / 12) squared)
Worked example
Pitch factors for common roofs, then one applied.
- 1.4/12: square root of (1 + 0.111) = 1.054
- 2.6/12: square root of (1 + 0.25) = 1.118
- 3.8/12: square root of (1 + 0.444) = 1.202
- 4.12/12: square root of (1 + 1) = 1.414
- 5.2,000 sq ft of plan area at 6/12: 2,000 x 1.118 = 2,236 sq ft
A 6/12 roof with 2,000 sq ft of plan area has 2,236 sq ft of roof surface to cover.
Measure it in MetreMate
Read the pitch from the roof plan notes, or measure the roof angle off an elevation with the Angle tool, then multiply your Area takeoff by the pitch factor.
See the Angle featureReady to measure smarter?
Upload your first plan and get accurate measurements in under 90 seconds. Free to start, no credit card needed.
Try MetreMate Today, It's Free!