How do you describe roof pitch?
Short answer. In the U.S., describe roof pitch as inches of rise per 12 inches of run, written 6/12 or 6:12 and spoken as six in twelve, or simply a six pitch. You can also give it in degrees (6/12 is about 26.6 degrees) or as percent slope (50 percent), but roofers, insurers, and building plans almost always use the x/12 form.
Ways pitch is written
- Ratio over 12: 4/12, 6/12, 8/12. The most common form on quotes, insurance estimates, and plans.
- Colon form: 6:12, same meaning.
- Spoken: "six in twelve," "six twelve," or just "a six" on a job site.
- Plan symbol: elevation drawings show a small right triangle with 12 on the horizontal leg and the rise on the vertical leg.
- Degrees: used in some product instructions and outside the U.S.
- Percent slope: rise over run times 100, used more for drainage and low-slope roofs.
General terms
- Flat or low slope: under about 3/12 or 4/12, depending on who is talking.
- Conventional or moderate: roughly 4/12 to 8/12.
- Steep: above about 8/12. Insurance estimates add steep labor charges starting around 7/12, and again at higher pitches.
Pitch versus slope
Strictly speaking, slope is rise over run, and traditional carpentry used pitch for rise over the full span, so a "quarter pitch" meant the rise was one quarter of the span, the same as 6/12. In everyday American roofing, the two words are used interchangeably for the x/12 number.
Be specific when it matters
When asking for quotes or reviewing an estimate, list the pitch of each roof section, such as "main roof 8/12, porch 3/12." See how roofers measure a roof and roof anatomy explained.