Roof pitch, also known as roof slope, is a crucial factor in roofing design and construction.

It determines how steep or shallow your roof is, and this measurement is essential for various reasons, including drainage, aesthetics, and material selection.

In this blog, we’ll simplify the process of calculating roof pitch size and explain why it’s important.

What Is Roof Pitch?

Roof pitch refers to the steepness or slope of a roof, typically expressed as a ratio of rise to run. The “rise” is the vertical measurement of how much the roof goes up, and the “run” is the horizontal measurement of how far the roof extends.

For example, if a roof rises 6 inches vertically for every 12 inches it extends horizontally, it has a 6/12 pitch, which can also be expressed as a 1/2 pitch.

Why Is Roof Pitch Important?

  1. Water Drainage: Roof pitch plays a significant role in directing rainwater and snowmelt away from your roof’s surface. Steeper pitches shed water faster and are more effective at preventing water damage.
  2. Aesthetics: Roof pitch affects the visual appearance of your home or building. It can give your structure a unique look and feel, enhancing its architectural style.
  3. Material Selection: The pitch of your roof influences the choice of roofing materials. Steeper pitches may require different materials than flatter ones to ensure proper waterproofing and durability.
  4. Snow and Debris Shedding: In regions with heavy snowfall, a steeper pitch helps prevent snow buildup, reducing the risk of roof damage.

How to Calculate Roof Pitch Size

Calculating roof pitch size can be done in a few simple steps:

Step 1: Measure the Rise and Run

Start by measuring the vertical rise of your roof. This is the distance from the highest point of the roof to the lowest point. Next, measure the horizontal run, which is the horizontal distance from one end of the roof to the other.

Step 2: Calculate the Pitch

To calculate the pitch, use the rise and run measurements. Divide the rise by the run. For example, if the rise is 6 inches and the run is 12 inches, the pitch is 6/12 or 1/2.

Step 3: Convert to a Pitch Angle

If you prefer to express the pitch as an angle, you can use a simple formula:

Pitch Angle (in degrees) = arctan(Rise / Run)

In our example, the pitch angle would be the arctan(6/12), which is approximately 26.57 degrees.

Examples of Roof Pitches

Now, let’s look at a few common roof pitch examples:

  1. Flat Roof: A flat roof has a pitch close to 0/12, meaning it has very little slope. This is common in modern architecture and commercial buildings.
  2. Low Slope Roof: A low slope roof typically ranges from 1/12 to 4/12. It’s often seen in residential homes with modern designs.
  3. Moderate Slope Roof: A moderate slope falls within the range of 4/12 to 9/12. This is a common pitch for traditional residential roofs.
  4. Steep Slope Roof: A steep slope roof can have pitches ranging from 9/12 and higher. It’s often used in areas with heavy snowfall and for aesthetics in certain architectural styles.

The Verdict: Know Your Roof Pitch

Understanding how to calculate and interpret roof pitch size is valuable when you’re planning a roofing project or purchasing a new home.

It helps you make informed decisions about materials, aesthetics, and drainage capabilities.

Whether you prefer a low-slope modern look or a steep-slope traditional style, knowing your roof pitch ensures your roof serves its purpose effectively and looks great while doing so.


As a civil engineer and roofer, I love to share the experience that I have gained through the last couple of years. In the roofing industry, practical experience is a very crucial fact that can help you a lot. Hence, I want to help you with my blog.

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