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Convert rise and run measurements, degrees, or grade percentages instantly to determine your roof's slope category and material requirements.
Measurement units must match (e.g., both inches or both feet).
While contractors generally say "Pitch" (like 4/12), architects, engineers, and framers sometimes define slope using degrees or percentages.
The standard roofing measurement in North America. It describes how many inches the roof rises vertically for every 12 inches it runs horizontally. Expressed as a fraction like 4/12.
The mathematical angle created by the slope of the roof intersecting with a perfectly horizontal line. A 12/12 pitch, which forms a perfect right triangle, equates exactly to a 45° angle.
Often used in construction site planning or civil engineering. It is simply Rise divided by Run, multiplied by 100. A roof that rises 6 inches over 12 inches (0.5) has a 50% grade.
Your roof's pitch dictates speed of water runoff. Using the wrong material on a specific pitch will almost always result in water backup and leaks.
Water moves slowly. Shingles will leak. Requires continuous membranes like highly-sealed EPDM rubber, TPO, PVC, or Built-Up Roofing (BUR/Tar & Gravel).
Asphalt shingles can be used, but building codes require special underlayment, typically two layers of felt paper or specialized ice-and-water shielding. Roll roofing and standing seam metal work well here.
The sweet spot. Safe for installers to walk on easily. Almost all roofing materials perform aggressively well here, especially standard 3-tab or architectural asphalt shingles.
Extremely fast runoff. Usually requires specialized roof jacks and harnesses to safely install. Heavy shingles may require over-nailing with 6 nails instead of 4 to prevent gravity from pulling them down over time.
Roof pitch is the relationship between vertical rise and horizontal run. It affects water drainage speed, material compatibility, structural loading, ventilation decisions, and long-term maintenance requirements.
Accurate pitch measurements help homeowners, roofers, and estimators avoid material failures, code issues, and pricing errors. One wrong assumption about slope can lead to leaks, underlayment problems, or unnecessary labor costs.
Pitch = Rise / Run
Standard form: X/12
Example: 6 inches rise over 12 inches run is a 6/12 pitch.
Angle (deg) = arctan(Rise / Run)
Grade (%) = (Rise / Run) x 100
These conversions are used in plan sets, engineering docs, and drainage calculations.
Rise/Run: 2/12
Angle: ~9.46°
Grade: 16.7%
Best with membrane or low-slope-rated metal systems.
Rise/Run: 6/12
Angle: ~26.57°
Grade: 50%
Works well with asphalt shingles and most standard materials.
Rise/Run: 10/12
Angle: ~39.81°
Grade: 83.3%
Higher labor and safety equipment requirements for installers.
Compare common pitch ranges to quickly understand roof category, drainage behavior, and material suitability.
| Pitch Range | Approx. Angle | Roof Type Signal | Typical Material Guidance |
|---|---|---|---|
| < 2/12 | < 9.5° | Flat / very low slope | Use membrane systems (TPO, EPDM, PVC). |
| 2/12 - 4/12 | 9.5° - 18.4° | Low slope | Special underlayment and low-slope-approved materials. |
| 4/12 - 9/12 | 18.4° - 36.9° | Conventional residential | Standard shingles and broad material compatibility. |
| > 9/12 | > 36.9° | Steep slope | Extra safety gear and fastening requirements often apply. |
| Pitch Range | Approx. Angle | Roof Type Signal | Typical Material Guidance | | --- | --- | --- | --- | | < 2/12 | < 9.5° | Flat / very low slope | Use membrane systems (TPO, EPDM, PVC). | | 2/12 - 4/12 | 9.5° - 18.4° | Low slope | Special underlayment and low-slope-approved materials. | | 4/12 - 9/12 | 18.4° - 36.9° | Conventional residential | Standard shingles and broad material compatibility. | | > 9/12 | > 36.9° | Steep slope | Extra safety gear and fastening requirements often apply. |
The most common residential roof pitch in the United States is between 4/12 and 9/12. These are considered "conventional" slopes because they look aesthetically pleasing, shed water well, and are relatively safe and easy for contractors to walk on during installation and repairs.
"4/12" means that for every 12 inches the roof runs horizontally toward the center of the house, it rises 4 inches vertically. It is the ratio of Rise over Run.
No. Traditional asphalt shingles rely on gravity to shed water over the courses below them. If the roof pitch is lower than 2/12, water will pool and run backward under the shingles, causing massive leaks. "Flat" or low-slope roofs (under 2/12) require continuous sealed membranes like EPDM rubber or TPO.
The safest way to measure pitch is from inside the attic. Place a 12-inch level horizontally against a roof rafter. Ensure it is perfectly level. Then, use a tape measure to check the vertical distance from the end of the 12-inch level straight up to the rafter. That vertical measurement is your "Rise", giving you a Rise/12 pitch.
Most standard standing seam or corrugated metal roofs require a minimum pitch of 3/12. Specifically designed mechanically seamed metal roofs can sometimes be installed on slopes as low as 1/12 or 2/12, but local building codes vary.
Pitches over 7/12 (approx. 30 degrees) are considered "steep" and usually incur extra labor charges. Installers cannot easily walk on them and must set up roof jacks, toe boards, and utilize fall protection harnesses. Pitches over 10/12 may incur even heavier safety surcharges.
Flat roofs require severe maintenance. Standing water (ponding) quickly breaks down roofing materials and increases the chance of leaks. Sloped roofs use gravity to instantly shed water, snow, and debris, making them last significantly longer with less maintenance.
Generally, yes. Steeper pitches shed water and snow much faster, reducing the time moisture sits on the shingles. They also catch less direct, prolonged UV sunlight in the summer compared to flatter surfaces, which helps prevent asphalt deterioration.
Find the tangent of the angle in degrees, and multiply the result by 12. For example, if your angle is 18.43°, tan(18.43) ≈ 0.333. Multiply by 12 = 4. Your pitch is 4/12.
These roof styles actually have two distinct pitches. A Gambrel (classic barn roof) has a shallow pitch near the top ridge, and drops off into a very steep pitch on the sides, maximizing attic storage space.
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