Free Roof Slope Tool
Roof Pitch Calculator
Enter a rise and run, a pitch like 6/12, or an angle in degrees. We'll convert it to every other format, give you the percent grade and the pitch multiplier for roof area, and tell you which roofing materials your slope allows. No signup, no email.
What do you know?
Hold a level flat against the roof or a rafter, mark 12 inches along it, and measure straight down (or up) to the roof surface. That vertical distance is your rise.
Or pick a common pitch
Enter the rise you measured to see your pitch, angle, and multiplier.
Example: 6/12 pitch
Once you enter a pitch, we'll tell you whether asphalt shingles and metal roofing are allowed, and whether the roof is walkable.
Don't know it? Measure your footprint by address.
Add your footprint to see the actual roof surface area: footprint × pitch multiplier.
How The Pitch Calculator Works
Roof pitch is the number of inches a roof rises for every 12 inches it runs horizontally. A 6/12 roof climbs 6 inches over each foot. Everything else comes from that one ratio:
- Pitch from rise and run: pitch = rise ÷ run × 12. A 9 inch rise over an 18 inch run is 6/12.
- Degrees: angle = arctan(pitch ÷ 12). A 6/12 roof is 26.6°.
- Percent grade: pitch ÷ 12 × 100. A 6/12 roof is a 50.0% grade, and a 12/12 roof is 100%.
- Pitch multiplier: √(1 + (pitch ÷ 12)²). Multiply your footprint by it to get the real roof surface. A 6/12 roof has 1.118 times more roof than footprint.
The material notes follow common building code and manufacturer minimums: standard asphalt shingle installs start at 4/12, shingles between 2/12 and 4/12 need double underlayment, and anything flatter than 2/12 is a low-slope roof that needs a membrane. Your specific shingle or panel may have its own rules, so a final call always comes from the product's install instructions.
Roof Pitch Chart
Every common roof pitch converted to degrees, percent grade, and the area multiplier. Multiply a footprint by the multiplier to get roof square footage.
| Pitch | Degrees | Percent grade | Multiplier | Category |
|---|---|---|---|---|
| 1/12 | 4.8° | 8.3% | 1.003 | Flat roof |
| 2/12 | 9.5° | 16.7% | 1.014 | Low slope |
| 3/12 | 14.0° | 25.0% | 1.031 | Low slope |
| 4/12 | 18.4° | 33.3% | 1.054 | Conventional slope |
| 5/12 | 22.6° | 41.7% | 1.083 | Conventional slope |
| 6/12 | 26.6° | 50.0% | 1.118 | Conventional slope |
| 7/12 | 30.3° | 58.3% | 1.158 | Conventional slope |
| 8/12 | 33.7° | 66.7% | 1.202 | Conventional slope |
| 9/12 | 36.9° | 75.0% | 1.250 | Conventional slope |
| 10/12 | 39.8° | 83.3% | 1.302 | Steep slope |
| 11/12 | 42.5° | 91.7% | 1.357 | Steep slope |
| 12/12 | 45.0° | 100.0% | 1.414 | Steep slope |
| 14/12 | 49.4° | 116.7% | 1.537 | Steep slope |
| 16/12 | 53.1° | 133.3% | 1.667 | Steep slope |
| 18/12 | 56.3° | 150.0% | 1.803 | Steep slope |
How To Measure Your Roof Pitch
You need two numbers: rise and run. Any of these three methods works, and the first two never require climbing onto the roof.
1. From the attic with a level and tape
Hold a level horizontally against the underside of a rafter. Mark the level at 12 inches from where it touches the rafter, then measure straight up from that mark to the bottom of the rafter. That distance is your rise, and your pitch is rise/12. This is the safest and most accurate method.
2. From a ladder at the roof edge
At the edge of the roof, set one end of a level on the roof surface, hold it level so it sticks out over the slope, and measure from the 12-inch mark straight down to the roof. If your level is shorter than 12 inches, use any run you can measure and enter both numbers in the Rise & Run mode above. The calculator scales it to X/12 for you.
3. From a photo or a phone app
Stand back from a gable end and take a photo looking straight at it. A free protractor or angle-finder app can measure the roofline angle in the photo, or you can lay your phone on a rafter in the attic and read the angle from its built-in level. Enter the degrees in the Angle mode to get the pitch. Expect this to be within about one pitch step (for example, 6/12 vs 7/12).
Once you have the pitch, pair it with our roof size calculator by address to get your total roof square footage and number of squares.
Common Roof Pitches In Denver
Denver's housing stock spans more than a century, and roof pitch tracks the era a home was built in. Here is what our crews see most often across the metro:
- 1950s to 1970s ranches (Lakewood, Arvada, Aurora, Westminster): usually 4/12 to 5/12. Low enough to walk, steep enough for a standard shingle install.
- Split-levels and bi-levels: mostly 4/12 to 6/12, sometimes with a 2/12 or 3/12 porch or addition roof that needs double underlayment or a membrane.
- 1990s and newer two-story homes (Highlands Ranch, Parker, Castle Rock, Thornton): typically 6/12 to 8/12, with lots of hips, valleys, and multiple pitches on one roof.
- Denver Squares, Tudors, and Victorians in older neighborhoods: Denver Squares have moderate hip roofs, while Tudors and Victorians often run 10/12 to 12/12 and steeper. Steep roofs shed snow well but take more labor and safety gear to replace.
- Modern infill and townhomes: flat or low-slope roofs under 2/12 with membranes, often mixed with low shed roofs. Standing seam metal roofing is a popular choice on these lower slopes.
For anything 4/12 and steeper, asphalt shingle roofing is the most common choice in Colorado, and Class 4 impact-resistant shingles hold up best against Front Range hail. Pitch also affects cost: steeper roofs have more surface area (that's the multiplier) and take longer to work on safely.
Frequently asked
Questions
Every home and homeowner is different, which is why clear communication is at the heart of what we do. To help you better understand our process, products, and what to expect when working with us, we've gathered a list of frequently asked questions and straightforward answers here.
SCHEDULE AN ESTIMATE →Want Us To Measure It For You?
A free, in-person inspection takes about 30 minutes. We measure every pitch, hip, and valley on your roof and give you a written estimate based on the real numbers.