Roof Pitch: What It Means and How to Find Yours
Roof pitch is how many inches a roof rises for every 12 inches it runs horizontally, written as a ratio like 4:12 or "4 in 12." California's residential code states slopes the same way, as units vertical in 12 units horizontal, sometimes with a percent. To convert: the angle in degrees is the arctangent of rise ÷ 12, so 4:12 is about 18.4 degrees and 6:12 about 26.6; the percent is rise ÷ 12 × 100, so 4:12 is 33 percent. You can find your own pitch from the attic with a level and a tape, or with an angle-finder app laid on a rafter, without going on the roof. Pitch decides which coverings are allowed (asphalt shingles need at least 2:12, tile at least 2½:12), how many layers of underlayment go down, and whether OSHA counts the roof as steep, which it does above 4 in 12.
Pitch, degrees and percent
Pitch converts to an angle and a percent with simple arithmetic.
| Pitch | Degrees | Percent slope |
|---|---|---|
| 2:12 | 9.5° | 16.7% |
| 2½:12 | 11.8° | 20.8% |
| 3:12 | 14.0° | 25% |
| 4:12 | 18.4° | 33.3% |
| 5:12 | 22.6° | 41.7% |
| 6:12 | 26.6° | 50% |
| 7:12 | 30.3° | 58.3% |
| 8:12 | 33.7° | 66.7% |
| 9:12 | 36.9° | 75% |
| 10:12 | 39.8° | 83.3% |
| 12:12 | 45.0° | 100% |
The code prints percentages next to some ratios, rounded; where a printed percent and the ratio disagree, go by the ratio. Its tile section, for example, pairs 2½:12 with "25-percent slope," while 2½ in 12 works out to about 21 percent.
How to find your roof's pitch
1. From the attic. Hold a level horizontally against the underside of a rafter, mark 12 inches along the level from where it touches the rafter, and measure straight up from that mark to the rafter. That measurement is the rise: 5 inches means a 5:12 pitch.
- With an angle finder. Lay an angle finder or a phone's angle app on a rafter, or on a gable end's trim, read the degrees, and convert with the table or with rise = 12 × tan(angle). A reading of 23 degrees is about 5:12.
- From the plans. House plans and permit drawings often show pitch on the sections or elevations, but a roof that's been altered may not match them.
- Not from the roof itself. Leave measuring on the roof to someone set up for it; OSHA treats any roof steeper than 4 in 12 as a steep roof for fall-protection purposes.
A house can have more than one pitch, such as a porch or an addition with a lower slope than the main roof, and each plane is measured separately.
What pitch decides
- Which coverings are allowed. Asphalt shingles need at least 2:12 (R905.2.2); clay and concrete tile at least 2½:12 (R905.3.2). Flatter roofs take low-slope coverings; the full table is in minimum roof slope by material.
- How much underlayment. Shingles get two layers from 2:12 up to 4:12 and one from 4:12 up, and tile gets a double layer from 2½:12 up to 4:12; see roof underlayment types.
- How tile is fastened. On battens, field tiles below 5:12 may go unfastened, every other row from 5:12, and every tile from 12:12 (R905.3.8); more in tile roofs and earthquakes.
- Safety. OSHA's fall-protection rules for construction define a low-slope roof as 4 in 12 or less and a steep roof as anything steeper.
- Roof area. A steeper roof has more surface over the same footprint, which is how roofers turn a footprint into squares; see how roofers measure a roof in squares.
- Solar. A flush-mounted array sits at the roof's angle, so the pitch is the panels' tilt.
What we've seen
On a North Hills solar job in April 2025, the crew set an angle finder on the plane before laying anything out, because the pitch sets the tilt toward the sun, the spacing between rows and what the crew needs to work safely; the pitch was measured on the plane, not taken from the plans (the North Hills case). On a Chatsworth roof in 2025–2026, every group of the array sits at 23 degrees, about a 5:12 pitch (the Chatsworth case).
Frequently asked
What does 4:12 pitch mean?
Can a roof have more than one pitch?
How do I measure roof pitch without going on the roof?
What pitch is too low for shingles?
Is a 6:12 roof steep?
Related reading
Sources & methodology
Code sections, rules and figures on this page come from the primary sources below. Codes, local requirements and product terms change; each was verified October 9, 2026.
We measure every roof plane before we quote
Call (323) 844-7777. We measure the pitch of each plane on the roof itself, not from the plans, and tell you which coverings and underlayment the slope allows. Have ready the address and, if you have them, the house plans.
Prepared by Cali Energy, October 9, 2026. This article is for general educational purposes only and is not legal, tax, financial, engineering, or utility advice. Rates, incentives, codes, permit requirements, equipment specifications, prices, and program terms may change; figures and timelines are estimates, not guarantees. Confirm current requirements with the applicable utility, AHJ, program administrator, manufacturer, or a licensed professional. See our Content Disclaimer. Cali Energy · 19201 Parthenia St, Unit E, Northridge, CA 91324 · CSLB #1032379 (B, C-10, C-39)