Roof Pitch vs Slope vs Angle
All three describe how steep a roof is. In everyday US roofing, "pitch" and "slope" both mean rise per 12 inches of run, like 6/12. Angle is the same steepness in degrees. Below are the conversions, plus an older textbook meaning of "pitch" that still trips people up.
The three terms
| Term | How it is written | What it measures | Who uses it |
|---|---|---|---|
| Slope (rise : run) | 6/12, 6:12, "6 in 12" | Inches of rise per 12 inches of horizontal run | Building codes, shingle and metal manufacturers |
| Pitch (everyday) | 6/12 or "a 6 pitch" | Same as slope in everyday use | Roofers, homeowners, suppliers |
| Pitch (traditional) | 1/4, 1/3, 1/2 | Total rise ÷ total span (the full building width) | Older carpentry texts, some exam questions |
| Angle | 26.57° | Degrees above horizontal | Engineers, solar installers, apps, Europe |
| Percent grade | 50% | Rise ÷ run × 100 | Low-slope commercial, civil work |
Conversions
Common slopes in every unit
| Slope | Angle | Percent | Traditional pitch | Area multiplier |
|---|---|---|---|---|
| 2/12 | 9.46° | 16.7% | 1/12 | 1.014 |
| 3/12 | 14.04° | 25% | 1/8 | 1.031 |
| 4/12 | 18.43° | 33.3% | 1/6 | 1.054 |
| 5/12 | 22.62° | 41.7% | 5/24 | 1.083 |
| 6/12 | 26.57° | 50% | 1/4 | 1.118 |
| 7/12 | 30.26° | 58.3% | 7/24 | 1.158 |
| 8/12 | 33.69° | 66.7% | 1/3 | 1.202 |
| 9/12 | 36.87° | 75% | 3/8 | 1.250 |
| 10/12 | 39.81° | 83.3% | 5/12 | 1.302 |
| 12/12 | 45.00° | 100% | 1/2 | 1.414 |
The full chart from 1/12 to 24/12 is on the pitch to degrees page, and the roof pitch calculator converts any rise and run.
Why the old "pitch" meaning matters
In traditional carpentry, pitch is rise divided by the whole span, so a 12/12 roof is a "1/2 pitch" and an 8/12 is a "1/3 pitch". You'll still see it in older plans, framing-square manuals and some licensing exam questions. If a document says "1/3 pitch", it means 8/12, not 4/12. When in doubt, ask for the rise per 12 inches of run. Nobody misreads that.
Which number matters for what
- Material rules (minimum slope for shingles, metal or membranes) are written as rise:12. See minimum pitch by material.
- Area and material quantities use the multiplier from the slope. See add for pitch.
- Rafter cuts use the angle: the plumb cut equals the roof angle. See the rafter length calculator.
- Solar tilt and snow load tables are usually in degrees.
A 45° roof is 12/12, not 45/12, and a 100% grade is 45°, not vertical. Mixing up degrees and percent is the most common conversion error.
Frequently asked questions
Is roof pitch the same as roof slope?
In everyday US roofing, yes. Both mean inches of rise per 12 inches of run, such as 6/12. Traditionally, pitch meant rise divided by the full span, so a 6/12 slope is a 1/4 pitch.
What angle is a 6/12 roof pitch?
26.57 degrees. The angle is the arctangent of rise divided by run: arctan(6/12).
How do I convert degrees to roof pitch?
Multiply the tangent of the angle by 12. For 30 degrees, 12 × tan(30°) = 6.93, which is about a 7/12 pitch.
What is a 1/3 pitch roof?
In the traditional rise-over-span system, a 1/3 pitch rises one third of the building width, which is an 8/12 slope (33.69 degrees).
What percent slope is a 4/12 roof?
33.3%, because 4 divided by 12 is 0.333.
Last reviewed 2026-10-10. Results are estimates for planning; confirm quantities with your supplier and requirements with your local building code and the manufacturer's instructions.