Learn about different calculator methods to calculate roof pitch and understand what each measurement means when using our roof pitch calculator tool
Roof pitch is the steepness or slope of a roof, typically expressed as a ratio of vertical rise to horizontal run. In the United States, it's commonly expressed as a ratio of rise over a 12-inch run (e.g., 4:12, 6:12).
Understanding roof pitch is crucial for:
Safe methods to measure roof pitch without climbing.
For best accuracy, measure directly on the roof with a level and tape measure.
The most common method for calculating roof pitch.
Rise: The vertical distance from the top of the wall to the peak of the roof
Run: The horizontal distance from the edge of the roof to the center (half the span)
Pitch = (Rise ÷ Run) × 12
Example: If rise = 6" and run = 12", then pitch = 6:12
Calculate pitch using the roof's angle in degrees.
This method is useful when you can measure the angle directly using a digital level or protractor. The angle is measured from the horizontal plane to the roof surface.
Pitch = tan(angle) × 12
Example: A 26.57° angle = 6:12 pitch
Common angles: 18.43° (4:12), 26.57° (6:12), 33.69° (8:12)
Express pitch as a simple ratio of rise to run.
This method allows you to input any rise and run measurements and convert them to the standard pitch notation (X:12 format).
Ratio = Rise : Run
Example: 1:2 ratio = 6:12 pitch
Slope is the general term for the incline or steepness of any surface, including roofs, roads, and ramps. It can be expressed in multiple ways:
Slope % = (Rise ÷ Run) × 100
Example: 6" rise ÷ 12" run = 0.5 = 50% slope
Pitch is a specific term used primarily in roofing. In North America, it's standardized to the X:12 format, where X is the rise over a 12-inch run.
Pitch = (Rise ÷ Run) × 12 : 12
Example: 4" rise ÷ 8" run = 0.5 × 12 = 6:12 pitch
💡 Key Takeaway:
Slope is the general concept (can be any ratio), while Pitch is the roofing industry's standardized way of expressing slope (always X:12 format). A 50% slope equals a 6:12 pitch, and both describe the same steepness.
A slope ratio expresses the relationship between vertical rise and horizontal run as a simple ratio. It's a universal way to describe steepness that works for any surface.
Rise = Run
• 45° angle
• 100% slope
• 12:12 pitch
• Very steep roof
Rise = Half of Run
• 26.57° angle
• 50% slope
• 6:12 pitch
• Common residential
Rise = One-third of Run
• 18.43° angle
• 33.33% slope
• 4:12 pitch
• Low slope roof
Ratio → Pitch: (Rise ÷ Run) × 12 = X in X:12
Ratio → Percentage: (Rise ÷ Run) × 100 = %
Ratio → Angle: arctan(Rise ÷ Run) = degrees
Example: If you measure a roof with 8" rise and 16" run, the slope ratio is 8:16 or simplified to 1:2. This converts to:
The standard notation showing how many inches the roof rises for every 12 inches of horizontal run. This is the most common way to express roof pitch in construction.
The angle of the roof slope measured from the horizontal. Useful for architectural drawings and when using angle-measuring tools.
The slope expressed as a percentage. A 100% slope means the rise equals the run (45° angle). Commonly used in civil engineering and road construction.
Used to calculate the actual length of roofing materials needed. Multiply the horizontal measurement by this number to get the sloped length. Essential for material estimation.
Nearly flat to gentle slope. Often requires special waterproofing. Common in commercial buildings.
Most common for residential roofs. Good balance of drainage, walkability, and material efficiency.
Steep roofs. Excellent drainage but require more materials and safety precautions during installation.