Roofing Tools
Roof Pitch Calculator
Roof pitch is how many inches a roof rises for every 12 inches it runs horizontally. Enter rise and run, an angle, or a percent grade to get the pitch, its angle, and the slope multiplier used to estimate roof area.
Results
Roof pitch
6/12
Conventional slope
- Angle
- 26.6°
- Percent grade
- 50%
- Slope multiplier
- 1.118
- Rise per foot of run
- 6 in
4/12 up to 7/12. The most common range for homes, and usually walkable with normal care.
How this was calculated
- Rise per 12 = 6 ÷ 12 × 12 = 6
- Angle = atan(6 ÷ 12) = 26.57°
- Percent grade = 6 ÷ 12 × 100 = 50%
- Multiplier = √(1 + (6 ÷ 12)²) = 1.118
How the formula works
All three input methods are converted to rise per 12 inches of run, then everything else is derived from that.
pitch = rise ÷ run × 12 (written as x/12) angle = atan(pitch ÷ 12) grade = pitch ÷ 12 × 100% multiplier = √(1 + (pitch ÷ 12)²)
Example
An attic measurement shows a rafter rising 7.5 inches over 12 inches of level. That is a 7.5/12 pitch: about 32.0 degrees, a 62.5% grade, and a multiplier of 1.179. A 1,600 sq ft footprint would have roughly 1,600 × 1.179 = 1,887 sq ft of roof surface.
Common roof pitches
| Pitch | Angle | Multiplier |
|---|---|---|
| 3/12 | 14.0° | 1.031 |
| 4/12 | 18.4° | 1.054 |
| 5/12 | 22.6° | 1.083 |
| 6/12 | 26.6° | 1.118 |
| 7/12 | 30.3° | 1.158 |
| 8/12 | 33.7° | 1.202 |
| 9/12 | 36.9° | 1.250 |
| 10/12 | 39.8° | 1.302 |
| 12/12 | 45.0° | 1.414 |
Limitations
- Results are only as accurate as your measurement. A small error in rise changes the multiplier on steep roofs.
- Many homes have more than one pitch. Measure each roof plane separately if they differ.
- Slope categories are general guidance. Material requirements come from local code and the manufacturer's instructions.
Common questions
What does a 6/12 roof pitch mean?
The roof rises 6 inches for every 12 inches of horizontal distance. That is about 26.6 degrees, a 50% grade, and a slope multiplier of about 1.118.
How do I measure my roof pitch without getting on the roof?
From inside the attic, hold a level horizontally against a rafter, mark 12 inches along the level, and measure straight up from that mark to the underside of the rafter. You can also measure a gable end from a ladder, or use a phone level app on a rake board to get the angle.
What is a roof pitch multiplier?
It converts flat (plan) area into sloped roof area. Multiply the building footprint, including overhangs, by the multiplier to estimate how much roof surface there actually is.
What is the minimum pitch for asphalt shingles?
Under the International Residential Code, asphalt shingles need a slope of at least 2/12, and roofs from 2/12 up to 4/12 require additional underlayment. Local codes and manufacturer instructions can be stricter.
Related tools
This tool provides an educational estimate only. Insurance companies, contractors, and building officials may calculate these figures differently depending on policy language, property condition, local pricing, and applicable codes.
Disclaimer: Calculators and information on this site are provided for educational and estimating purposes only. Results do not determine insurance coverage, claim payments, repair requirements, or professional recommendations.