Calculators for this guide
What roof pitch means
Pitch is the rise of the roof in inches for every 12 inches of horizontal run, written as a ratio like 6/12 ("six in twelve"). A 6/12 roof rises 6 in for every foot it extends horizontally. Some people express it as an angle instead; both describe the same slope.
How to measure pitch
- From the attic (safest): hold a level horizontally against the underside of a rafter, mark 12 in along the level, and measure straight up from that mark to the rafter. That measurement is the pitch.
- From a ladder at the gable: the same method works against the rake edge — never stand on a steep roof to measure.
- From the ground: smartphone angle apps can read the slope from a photo of the gable; convert the angle with the chart below.
Pitch to angle conversion
| Pitch | Angle | Area multiplier |
|---|---|---|
| 2/12 | 9.5° | 1.014 |
| 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 |
The multiplier tells you how much more surface the roof has than the flat footprint beneath it — the key to estimating shingles.
Why pitch matters
- Material quantity: a 12/12 roof has about 41% more surface than its footprint; a 4/12 roof only about 5% more.
- Which roofing you can use: under the IRC, asphalt shingles are allowed on slopes of 2/12 or steeper, and slopes from 2/12 up to 4/12 need double underlayment. Flatter roofs need membrane systems.
- Safety and labor: roofs steeper than about 7/12 usually need roof jacks or harnesses, which raises installation cost.
- Solar: panel output depends on tilt and orientation; moderate pitches facing south work well in most of the US.