Roof Pitch Chart: Angles in Degrees, Slope & Multiplier
By Marko VisicBSc Physics, University of Ljubljana
Roofers talk in pitch; phone apps, plans and solar specs give degrees. This chart converts every pitch from 1/12 to 24/12, with the multiplier that turns a footprint into roof area.
A roof pitch chart turns rise per 12 of run into an angle. A 4/12 pitch is 18.4 degrees, 6/12 is 26.6 degrees and 12/12 is 45. Each pitch also has a slope in percent and a multiplier: a 6/12 roof has 1.118 square feet of roof over each square foot of floor.
18.4°
the angle of a 4/12 roof pitch
Roof pitch chart, 1/12 to 24/12
Pitch is the rise in inches for each foot of level run, so the first column also reads as inches per foot. The angle and the slope describe the same tilt in degrees and percent; the multiplier is the length along the roof for each unit of run, and the area column applies it to a footprint.
| Pitch | Angle | Slope | Multiplier | Roof per 100 sq ft of footprint | OSHA class |
|---|---|---|---|---|---|
| 1/12 | 4.8° | 8.3% | 1.003 | 100 sq ft | Low-slope |
| 2/12 | 9.5° | 16.7% | 1.014 | 101 sq ft | Low-slope |
| 3/12 | 14.0° | 25% | 1.031 | 103 sq ft | Low-slope |
| 4/12 | 18.4° | 33.3% | 1.054 | 105 sq ft | Low-slope |
| 5/12 | 22.6° | 41.7% | 1.083 | 108 sq ft | Steep |
| 6/12 | 26.6° | 50% | 1.118 | 112 sq ft | Steep |
| 7/12 | 30.3° | 58.3% | 1.158 | 116 sq ft | Steep |
| 8/12 | 33.7° | 66.7% | 1.202 | 120 sq ft | Steep |
| 9/12 | 36.9° | 75% | 1.250 | 125 sq ft | Steep |
| 10/12 | 39.8° | 83.3% | 1.302 | 130 sq ft | Steep |
| 11/12 | 42.5° | 91.7% | 1.357 | 136 sq ft | Steep |
| 12/12 | 45.0° | 100% | 1.414 | 141 sq ft | Steep |
| 14/12 | 49.4° | 116.7% | 1.537 | 154 sq ft | Steep |
| 16/12 | 53.1° | 133.3% | 1.667 | 167 sq ft | Steep |
| 18/12 | 56.3° | 150% | 1.803 | 180 sq ft | Steep |
| 20/12 | 59.0° | 166.7% | 1.944 | 194 sq ft | Steep |
| 24/12 | 63.4° | 200% | 2.236 | 224 sq ft | Steep |
To check a roof of your own, the roof pitch calculator works the same numbers from a measured rise and run, an angle, or the building’s width.
Degrees to roof pitch
Phone inclinometers, plans and solar mounting specs often give the angle instead. Twelve times the tangent of the angle is the pitch; the nearest whole pitch is what a roofer would call it.
| Angle | Pitch (rise per 12) | Nearest whole pitch | Slope |
|---|---|---|---|
| 5° | 1.05 | 1/12 | 8.7% |
| 10° | 2.12 | 2/12 | 17.6% |
| 15° | 3.22 | 3/12 | 26.8% |
| 20° | 4.37 | 4/12 | 36.4% |
| 25° | 5.60 | 6/12 | 46.6% |
| 30° | 6.93 | 7/12 | 57.7% |
| 35° | 8.40 | 8/12 | 70% |
| 40° | 10.07 | 10/12 | 83.9% |
| 45° | 12.00 | 12/12 | 100% |
| 50° | 14.30 | 14/12 | 119.2% |
| 55° | 17.14 | 17/12 | 142.8% |
| 60° | 20.78 | 21/12 | 173.2% |
Low slopes in inches per foot
Below 2/12 roofs are usually specified in inches per foot or in percent rather than as a pitch, because the numbers get small. A quarter inch per foot, the least design slope the 2021 IRC allows for drainage on built-up and modified bitumen roofs, is only about 1.2 degrees.
| Pitch | Inches per foot | Slope | Angle |
|---|---|---|---|
| ⅛/12 | ⅛ in | 1.04% | 0.60° |
| ¼/12 | ¼ in | 2.08% | 1.19° |
| ½/12 | ½ in | 4.17% | 2.39° |
| 1/12 | 1 in | 8.33% | 4.76° |
| 2/12 | 2 in | 16.67% | 9.46° |
Common pitches, one by one
2/12 roof pitch: 9.5 degrees
2 inches of rise per foot · 16.7% slope · 101 sq ft of roof per 100 sq ft of footprint · low-slope under OSHA
The 2021 IRC allows asphalt shingles from here up, with double underlayment from 2/12 up to 4/12; solar shingles also start at 2/12.
3/12 roof pitch: 14.0 degrees
3 inches of rise per foot · 25% slope · 103 sq ft of roof per 100 sq ft of footprint · low-slope under OSHA
Wood shingles and shakes start at 3/12, as do metal roof shingles (3/12) and lapped metal panels without sealant (3/12). Asphalt shingles and tile still need double underlayment here.
4/12 roof pitch: 18.4 degrees
4 inches of rise per foot · 33.3% slope · 105 sq ft of roof per 100 sq ft of footprint · low-slope under OSHA
Slate starts at 4/12, and 4/12 is where the code’s double-underlayment ranges for asphalt shingles and clay or concrete tile (from 2½/12) end.
5/12 roof pitch: 22.6 degrees
5 inches of rise per foot · 41.7% slope · 108 sq ft of roof per 100 sq ft of footprint · steep under OSHA
The first whole pitch OSHA treats as steep: anyone working 6 feet or more above a lower level needs guardrails with toeboards, a safety net or a personal fall arrest system.
6/12 roof pitch: 26.6 degrees
6 inches of rise per foot · 50% slope · 112 sq ft of roof per 100 sq ft of footprint · steep under OSHA
A 30-foot-wide gable at this pitch has its ridge 7.5 feet above the wall tops, with a 16.77-foot rafter on each side.
8/12 roof pitch: 33.7 degrees
8 inches of rise per foot · 66.7% slope · 120 sq ft of roof per 100 sq ft of footprint · steep under OSHA
Each foot of run is 1.202 feet along the roof, so a rafter over a 15-foot run is 18.03 feet long.
10/12 roof pitch: 39.8 degrees
10 inches of rise per foot · 83.3% slope · 130 sq ft of roof per 100 sq ft of footprint · steep under OSHA
At this angle the roof stands about 5.2 degrees short of a 45-degree roof.
12/12 roof pitch: 45.0 degrees
12 inches of rise per foot · 100% slope · 141 sq ft of roof per 100 sq ft of footprint · steep under OSHA
Rise equals run: the roof sits at 45 degrees and has about 41% more area than its footprint.
Roof pitch chart FAQ
What does 6 on 12 mean on a roof?
It is the pitch: the roof rises 6 inches for every 12 inches of level run, also written 6/12 or 6:12. That is 26.6 degrees and a 50% slope.
Is a 12/2 roof pitch the same as 2/12?
Yes. Some people write the run first, so 12/2 and 2/12 both mean 2 inches of rise in 12 of run: 9.5 degrees and a 16.7% slope. Pitch is stated per 12 of run, so the 12 is the run and the other number is the rise.
What pitch is a 30-degree roof?
About a 7/12. Twelve times the tangent of 30 degrees is 6.93, so a 30-degree roof rises that many inches per foot of run.
What pitch is a 45-degree roof?
A 12/12: the rise equals the run. Every foot of run takes 1.414 feet of roof, about 41% more than at flat.
How do I convert degrees to roof pitch?
Multiply 12 by the tangent of the angle. A 20-degree roof is 4.37/12, a little steeper than 4/12. To go from pitch to degrees, divide the rise by 12 and take the arctangent.
Sources & method
Angles, slopes and multipliers are trigonometry from the rise per 12 of run: angle = arctan(rise ÷ 12), slope = rise ÷ 12 × 100, multiplier = √(1 + (rise ÷ 12)²). Code minimums are from the 2021 International Residential Code, Section R905, and the low-slope and steep definitions from OSHA.
- International Code Council. 2021 IRC Chapter 9 Roof Assemblies, Section R905 Requirements for Roof Coverings. 2021 IRC
- U.S. Department of Labor, Occupational Safety and Health Administration. 29 CFR 1926.500(b) Definitions (Subpart M, Fall Protection). 29 CFR Part 1926 Subpart M, current text on osha.gov
- U.S. Department of Labor, Occupational Safety and Health Administration. 29 CFR 1926.501(b)(11) Steep roofs. 29 CFR Part 1926 Subpart M, current text on osha.gov
- Roof Pitch Calculator: Degrees, Slope & Roof HeightPitch from a rise and run, an angle or a building’s width, with the roofing the code allows.
- Roof Square Footage Calculator: Area & Roofing SquaresRoof surface and roofing squares from the footprint, overhang and pitch.
- Roof Pitch: What It Means & the Minimum for Each RoofingThe lowest pitch the 2021 IRC allows for every roofing, and pitch vs slope.
Marko Visic
I'm Marko Visic, a physics graduate who builds data-driven calculators. I run ConstructionCalc through my company, Moving Data Systems d.o.o.
The calculators help you plan a DIY job or check a contractor's quote before you sign. Each one cites its sources and shows its method, and cost figures are computed from public primary data. If a number looks wrong, email info@constructioncalc.org and I'll trace it to its source or fix it.