What's Your Roof Pitch?
Enter your rise and run — get the pitch (x:12), angle in degrees, percent grade, and slope factor in one shot.
Last updated: June 13, 2026
Common Pitches
Run is normally 12 in. Enter the rise over a 12-inch run, or your measured total rise and run in the same unit.
Get actual roof area
Pitch Results
6:12
roof pitch
26.57°
angle
50%
percent
1.118
slope factor
Conventional-slope roof
The slope factor turns your roof's footprint into actual roofing area —
Worked Examples
4:12 — Low-Slope Porch Roof
- Rise 4 in over 12 in run → slope 4 ÷ 12 = 0.333
- Angle: arctan(0.333) = 18.43°, or 33.3% grade
- Slope factor 1.054 — a 1,000 sq ft footprint is ~1,054 sq ft of roof
6:12 — Most Common House Pitch
- Rise 6 in over 12 in run → slope 0.5
- Angle 26.57°, 50% grade
- Slope factor 1.118 — 1,500 sq ft footprint = 1,677 sq ft of roofing
12:12 — Steep Gable
- Rise 12 in over 12 in run → slope 1.0
- Angle 45°, 100% grade
- Slope factor 1.414 — steep roofs add over 40% more surface than the footprint
Roof Pitch Reference Chart
| Pitch | Angle | Percent | Slope Factor |
|---|---|---|---|
| 1:12 | 4.76° | 8.3% | 1.003 |
| 2:12 | 9.46° | 16.7% | 1.014 |
| 3:12 | 14.04° | 25% | 1.031 |
| 4:12 | 18.43° | 33.3% | 1.054 |
| 5:12 | 22.62° | 41.7% | 1.083 |
| 6:12 | 26.57° | 50% | 1.118 |
| 7:12 | 30.26° | 58.3% | 1.158 |
| 8:12 | 33.69° | 66.7% | 1.202 |
| 9:12 | 36.87° | 75% | 1.25 |
| 10:12 | 39.81° | 83.3% | 1.302 |
| 11:12 | 42.51° | 91.7% | 1.357 |
| 12:12 | 45° | 100% | 1.414 |
Multiply your roof's footprint area by the slope factor to get the actual surface area for ordering materials.
Standard Pitch Ranges
| Range | Pitch | Typical Use |
|---|---|---|
| Flat / low-slope | < 2:12 | Needs membrane roofing (EPDM, TPO, built-up); not for shingles |
| Low-slope | 2:12 – 4:12 | Shingles allowed with extra underlayment; common on porches and additions |
| Conventional | 4:12 – 9:12 | Standard asphalt shingles; most U.S. homes fall here |
| Steep-slope | > 9:12 | Sheds water fast; common on Victorians, chalets, and gables |
Frequently Asked Questions
Roof pitch is the rise (vertical height) over the run (horizontal distance), written as rise:12. Divide the rise by the run to get the slope, then multiply by 12. A roof that rises 6 inches over 12 inches of run is a 6:12 pitch. Enter your rise and run above and the calculator gives you the pitch, angle, percent, and slope factor at once.
A 4:12 pitch is 18.43°, and a 6:12 pitch is 26.57°. To convert any pitch to degrees, take the arctangent of rise ÷ run. The Roof Pitch Reference Chart below lists the angle, percent grade, and slope factor for every pitch from 1:12 to 12:12.
The slope factor (also called the roof pitch multiplier) converts the flat area your roof covers into the actual sloped surface area. It equals the square root of ((rise ÷ run)² + 1). A 6:12 roof has a slope factor of 1.118, so a roof covering 1,500 sq ft on the ground is really about 1,677 sq ft of roofing surface. This is the number you need to order the right amount of shingles.
The easiest way: set a level against the roof or a rafter, measure 12 inches along the level, then measure straight down from the 12-inch mark to the roof. That down measurement is your rise over a 12-inch run. You can also use a speed square and torpedo level on the gable edge, or measure the total rise and run inside the attic. Enter whatever rise and run you measured — they don't have to be in 12-inch units.
Most U.S. homes fall between 4:12 and 9:12, the conventional-slope range that works with standard asphalt shingles. Anything below 2:12 is treated as flat and needs membrane roofing, while pitches steeper than 9:12 are considered steep-slope and shed water and snow quickly.
Measure the footprint your roof covers (length × width of the area under the roof), then multiply by the slope factor. Turn on "Get actual roof area" above and enter the footprint — the calculator applies the slope factor for you. Take that actual area to the roofing calculator to estimate shingle bundles.
They all describe the same steepness in different units. Pitch is the rise over a 12-inch run (6:12). Slope is the same ratio as a percent (50%). Angle is the steepness in degrees (26.57°). Builders usually talk in pitch; architects and tools often use degrees.
Yes. A shed, lean-to, or single-slope roof has just one rise and one run — measure those and enter them like any other roof, and the pitch, angle, and slope factor all apply. It works in metric too: enter rise and run in centimeters or meters as long as both use the same unit, since pitch and slope factor are ratios.