Roof Pitch, Angle & Area Calculator
Pitch is the rise in inches for every 12 inches of run: a 6 in 12 roof has a 26.57° angle, a 50% slope and a slope factor of 1.118, so a 40 × 28 ft footprint is 1,252.2 sq ft of roof.
Example: replace these measurements
Your roof measurements
6 in 12 roof pitch
6 in 12 roof pitch
1,252.2 sq ft measured
Your measured layout
- 6 in 12 roof pitch
Quantities and package details
- Angle
- 26.57°
- Slope
- 50%
- Slope factor
- 1.118
- Sloped roof area
- 1,252.2 sq ft
The calculation
- 6 ÷ 12 × 12 = 6 in 12
- 1,120 sq ft × 1.118 = 1,252.2 sq ft
Common questions
What does a 6/12 roof pitch mean?
The roof rises 6 inches for every 12 inches it runs horizontally. That is a 50 percent slope and an angle of about 26.6 degrees.
How do I convert roof pitch to degrees?
Divide the rise by the run and take the arctangent. A 4/12 roof is about 18.4 degrees and an 8/12 roof about 33.7 degrees. The calculator works in both directions, from pitch, angle or percent.
What is the slope factor?
The number that turns a flat footprint into sloped roof area: the sloped length over 12 inches of run, divided by 12. At 6/12 it is about 1.118, so a 1,000 sq ft footprint has about 1,118 sq ft of roof.
What is the lowest pitch for shingles?
GAF gives 2 in 12 as the absolute minimum slope for shingles, with extra underlayment on low slopes. Below that, plan a low-slope roof covering.
Source: GAF: Minimum slope for shingles. Listed on the Sources page.
How to plan the quantity
Rise is the vertical change over the horizontal run on the same roof plane. Enter both in inches. A measured rafter length is the slope, not the run.
Pitch compares vertical rise with horizontal run. The slope factor is the hypotenuse divided by the run. It converts a horizontal footprint into roof surface area.
Before you order
- This describes a single pitch. Split a roof with several pitches into separate sections.
- Use measurements from plans or a professional. This page does not select roofing suitable for the slope or require you to access the roof.
Before ordering, read the guide: How many bundles of shingles do I need? Squares, waste and accessories. Or choose another calculator.