Roof Pitch Calculator
Understanding Roof Pitch
Roof pitch is a numerical measure of the steepness of a roof. In the construction industry, it is typically expressed as a ratio of the vertical "rise" to the horizontal "run." For example, a "4/12 pitch" means the roof rises 4 inches for every 12 inches of horizontal distance.
How to Use the Roof Pitch Calculator
To calculate your roof's steepness, you need two primary measurements:
- Rise: The vertical height from the base of the roof section to the peak.
- Run: The horizontal distance from the edge of the roof to the point directly beneath the peak.
Once you enter these values, the calculator provides the pitch ratio, the angle in degrees, and the roof factor (useful for calculating rafter lengths and total surface area).
Common Roof Pitch Categories
| Category | Pitch Range | Common Materials |
|---|---|---|
| Flat Roof | 0/12 to 2/12 | TPO, EPDM, Built-up Roofing |
| Low Slope | 2/12 to 4/12 | Metal panels, specialized shingles |
| Conventional | 4/12 to 9/12 | Asphalt shingles, Tile, Slate |
| Steep Slope | 9/12 and up | Wood shakes, Slate, High-end shingles |
Why Pitch Matters
The pitch of your roof dictates more than just aesthetics. It influences:
- Water Drainage: Steeper roofs shed water and snow much faster, reducing the risk of leaks and structural weight from snow accumulation.
- Material Selection: Standard asphalt shingles generally require a minimum pitch of 2/12 or 4/12 to prevent water from backing up under the shingles.
- Maintenance: Steeper roofs are more difficult and dangerous to walk on, often requiring specialized safety equipment for repairs.
- Longevity: Generally, steeper roofs last longer because they dry faster and are less prone to debris buildup.
Example Calculation
If your roof rises 6 feet over a horizontal span of 12 feet:
- Rise: 6
- Run: 12
- Calculation: (6 / 12) * 12 = 6.
- Result: You have a 6/12 pitch, which corresponds to an angle of approximately 26.57 degrees.