Roof Pitch Calculator
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).
Pitch Results
Understanding Pitch vs. Angle vs. Grade
While contractors generally say "Pitch" (like 4/12), architects, engineers, and framers sometimes define slope using degrees or percentages.
Pitch (Rise over Run)
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.
Angle (Degrees)
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.
Grade (Percentage)
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.
Why Pitch Matters for Roofing Materials
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.
< 2/12 Pitch Flat Roofs
Water moves slowly. Shingles will leak. Requires continuous membranes like highly-sealed EPDM rubber, TPO, PVC, or Built-Up Roofing (BUR/Tar & Gravel).
2/12 - 4/12 Low Slope
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.
4/12 - 9/12 Conventional
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.
> 9/12 Pitch Steep Slope
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.
Frequently Asked Questions
What is a "Standard" roof pitch?
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.
What does 4/12 pitch actually mean?
"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.
Can I put asphalt shingles on a flat roof?
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.
How do I safely measure my roof pitch?
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.
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