Quick definition
The steepness of a roof, usually expressed as inches of vertical rise per 12 inches of horizontal run, such as 6:12.
Roof pitch tells you how steep a roof is. It affects which materials can be used, how well the roof drains, how safe it is to walk on, and how much the roof costs.
What is roof pitch?
Roof pitch is usually written as the inches a roof rises for every 12 inches it runs horizontally. A 6:12 roof (said "six in twelve") climbs 6 inches for every foot across. Some references define pitch as rise over the full span and slope as rise over run, but in everyday roofing the terms are used interchangeably.
Roof pitch chart
| Pitch | Angle | Area multiplier | Category |
|---|---|---|---|
| 2:12 | 9.5° | 1.014 | Low slope |
| 3:12 | 14.0° | 1.031 | Low slope |
| 4:12 | 18.4° | 1.054 | Steep slope |
| 6:12 | 26.6° | 1.118 | Steep slope |
| 8:12 | 33.7° | 1.202 | Steep slope |
| 12:12 | 45.0° | 1.414 | Steep slope |
The area multiplier converts a roof's flat footprint into its actual surface area. A 2,000-square-foot footprint at 6:12 has about 2,236 square feet of roof surface.
:::technical-note NRCA generally classifies roofs with a slope of 3:12 or less as low-slope and steeper roofs as steep-slope. Roofing materials are tested and warranted for specific minimum slopes. :::
Why does roof pitch matter?
- Materials: asphalt shingles, tile and some metal panels have minimum slopes. Low-slope roofs need membranes such as TPO or EPDM.
- Drainage: steeper roofs shed water and snow faster.
- Safety and labor: steep roofs need extra fall protection and take longer to work on, which raises the cost.
- Measurement: pitch determines how much roof area, and how many squares of material, a job needs.
How is roof pitch measured?
- On the roof: hold a level horizontally against the roof, measure 12 inches along it, and measure straight down to the roof surface. That number is the rise.
- From the attic: do the same against the underside of a rafter.
- From photos: aerial measurement reports and smartphone apps estimate pitch for each roof plane.
What it means for you
What Roof Pitch means for homeowners
Your roof's pitch helps decide which materials you can choose and why quotes differ. Steeper roofs usually cost more because of the extra area, safety equipment and labor.
Frequently asked questions
Sources
- The NRCA Roofing Manual. NRCA.
Tier 2 authority · industry - Roofing material manufacturer minimum slope requirements. Technical Reference.
Tier 1 authority · manufacturer - International Residential Code, Chapter 9: Roof Assemblies. International Code Council.
Tier 1 authority · code