Use the chart below to compare roof pitch, angle, percent slope, and roofing material options. A roof that rises 6 inches for every 12 inches of horizontal run has a 6:12 pitch, a 26.6-degree angle, and a 50% slope. These numbers describe the same roof in three different ways.
This roof pitch calculator chart covers whole-number pitches from 1:12 to 12:12. If your measurement falls between rows, such as 5.5:12, keep that value and use the calculator for the conversion. Do not round up when checking whether a roof meets a product’s minimum slope.
Roof pitch from 1:12 through 12:12
Find your rise per 12 inches of horizontal run in the first column, then read across for the angle, percentage, example uses, and material options to discuss with your roofer.
On a phone, swipe the table sideways to see every column.
| Pitch | Angle | Slope | Typical uses (examples) | Recommended roofing material options* |
|---|---|---|---|---|
| 1:12 | 4.8° | 8.3% | Low-profile porch or addition | A complete low-slope membrane system; no asphalt shingles |
| 2:12 | 9.5° | 16.7% | Shallow shed or porch roof | Low-slope membrane; approved shingles with low-slope underlayment |
| 3:12 | 14.0° | 25.0% | Low-profile residential roof | Approved shingles with low-slope underlayment; metal rated for 3:12 |
| 4:12 | 18.4° | 33.3% | Moderate residential gable or hip | Asphalt shingles; rated metal; clay or concrete tile* |
| 5:12 | 22.6° | 41.7% | Residential gable or hip | Asphalt shingles; rated metal; clay or concrete tile* |
| 6:12 | 26.6° | 50.0% | Residential main roof or garage | Asphalt shingles; rated metal; clay or concrete tile* |
| 7:12 | 30.3° | 58.3% | Taller gable with more roof rise | Asphalt shingles; rated metal; clay or concrete tile* |
| 8:12 | 33.7° | 66.7% | Prominent gable or dormer | Asphalt shingles; rated metal; clay or concrete tile* |
| 9:12 | 36.9° | 75.0% | Tall residential gable | Asphalt shingles; rated metal; clay or concrete tile* |
| 10:12 | 39.8° | 83.3% | Steep architectural gable | Asphalt shingles; rated metal; tile with specified fastening* |
| 11:12 | 42.5° | 91.7% | Tall dormer or accent roof | Asphalt shingles; rated metal; tile with specified fastening* |
| 12:12 | 45.0° | 100.0% | 45-degree gable or accent roof | Asphalt shingles; rated metal; tile with specified fastening* |
*These are starting options, not product approvals or an exhaustive list. Follow the selected system’s slope, underlayment, fastening, and local code requirements. Tile also requires adequate structural support. The example uses describe possible roof forms, not rules tying a building type to one pitch.
Read and convert rise and run
Identify the horizontal run and vertical rise
Run is the horizontal distance across the triangle. Rise is the vertical change at the end of that distance. The sloping roof surface forms the diagonal. At 6:12, a 12-inch run and a 6-inch rise produce a diagonal length of about 13.42 inches. Using that diagonal as the run would give an incorrect pitch.
The same ratio works in feet. Over a 10-foot horizontal run, a 6:12 roof rises 5 feet. On a symmetrical gable with a 20-foot wall-to-wall span, the run from one exterior wall to the ridge centerline is typically 10 feet, not 20. Overhangs add roof area beyond those walls.
Convert a run that is not 12 inches
Divide rise by horizontal run, using the same units for both. Multiply the result by 12 to get rise per 12 inches, or by 100 to get percent slope. To find the angle, take the arctangent of the rise/run ratio and express the result in degrees. Multiplying a percentage by 90 will not give the correct angle.
Suppose you measure 9 inches of rise over 24 inches of horizontal run. The ratio is 9 ÷ 24 = 0.375. That gives a 4.5:12 pitch, a 37.5% slope, and an angle of about 20.6 degrees. The roof pitch calculatoraccepts the original 9-inch and 24-inch measurements, so you can enter them directly.
Match roofing materials to the measured pitch
1:12 to 3:12: pay attention to water protection
At 1:12, use a roof covering intended for low-slope service, such as a complete modified-bitumen membrane assembly. For example, GAF’s LIBERTY system is rated for use at 1:12. A roll of underlayment alone is not a finished roof system.
Asphalt shingles begin at 2:12, subject to the product instructions. From 2:12 up to, but not including, 4:12, GAF’s low-slope guidance calls for additional underlayment protection. Do not read the 2:12 row as permission to use the same assembly as a 6:12 roof.
4:12 and above: more options, still product-specific
Asphalt shingles, suitable metal panels, and properly supported clay or concrete tile are possible options. Metal roofing requirements vary by product. For example, ASC’s Skyline Roofing lists a 3:12 minimum. Verify the exact panel profile rather than assuming any standing-seam panel is suitable for a shallow roof.
Tile brings separate weight and attachment requirements. The DOE tile roofing guide discusses these details. A chart cannot establish whether existing framing can carry a replacement material or which fastening pattern is required for your roof’s slope and wind exposure.
Estimate roof surface area from pitch
Roof surface area exceeds its horizontal projection. At 6:12, the multiplier is about 1.118; a 1,000-square-foot projected roof area becomes about 1,118 square feet of sloping surface. At 12:12, the multiplier is about 1.414, giving about 1,414 square feet over the same footprint. These figures are rounded for comparison; use the calculator’s full precision for your estimate.
Measure the roof’s projected boundary, including overhangs, rather than copying a home’s advertised living area. A two-story house with 2,000 square feet of living space might have a much smaller roof footprint. Divide a roof with different pitches into separate sections, apply the correct slope factor to each projected area, and add the resulting surface areas together.
Measured surface area is the starting point for a material order. Allow separately for cutting waste, valleys, starter strips, and ridge caps. Write down the pitch and projected area for each roof section before comparing estimates; that makes a 3:12 porch and a 7:12 main roof much harder to mix up.
A few helpful answers
Roof pitch, explained
What is a 4/12 roof pitch in degrees?
A 4/12 roof pitch has an angle of about 18.4 degrees and a slope of 33.3%. That means 4 inches of vertical rise for every 12 inches of horizontal run. The 4 is an inch measurement, not an angle.
Is a 6/12 roof pitch the same as a 50% slope?
Yes. Six divided by twelve is 0.5, so the slope is 50%. Its angle is about 26.6 degrees. Percentage and degrees describe the same roof but use different scales.
Why does a 12/12 roof have a 100% slope instead of 90 degrees?
A 100% slope means rise equals horizontal run. That forms a 45-degree angle. A vertical, 90-degree surface has zero horizontal run, so its pitch and percent slope are undefined.
Can I put asphalt shingles on a 1/12 roof?
No. Standard asphalt shingles require at least a 2:12 slope, with special underlayment below 4:12. For a 1:12 roof, discuss a complete membrane system rated for that slope and substrate with your roofer.
What if my measured pitch is between two chart rows?
Keep the actual measurement. For example, 5.5 inches of rise over 12 inches of run is 5.5:12, about 24.6 degrees. Use the calculator for an exact conversion; never round up to satisfy a material’s minimum slope.