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How To Calculate Roof Pitch

Lowe's Editorial Team

By Lowe's Editorial Team
Published January 29, 2025

Calculating the pitch of a roof might sound like something best left to the professionals, but with a little guidance, you can do it too. Knowing your roof’s pitch can help during renovations or adding extensions. Here, let’s break down how to calculate roof pitch using a few simple steps.

Tools and Materials

Materials

  • Pencil And Paper

What Is Roof Pitch

Before you understand how to calculate roof pitch, let us learn what roof pitch is. Roof pitch is simply a way to describe how steep a roof is. It is calculated by measuring how many inches the roof goes up (its rise) for every 12 inches it goes across (its run). For example, if a roof goes up 6 inches for every 12 inches it goes across, it has a 6:12 pitch. This measurement helps in understanding how a roof is designed and is important for things like drainage and choosing the right materials.

Steps To Calculate Roof Pitch

Measuring the pitch of your roof from the inside of your attic can give you valuable information about the slope of your roof without having to climb onto the roof itself. Follow these detailed steps for a safe and accurate measurement.

Caution

You can measure the pitch from either inside your attic or by climbing onto the roof. Ensure you are taking proper precautions, whichever method you choose.

How Roof Pitch Impacts Your Home

The pitch of your roof significantly influences your home’s overall look and function. A steeper pitch offers better water drainage and snow shedding which can prolong the roof’s lifespan. It also provides more attic space, potentially adding storage or living areas. Conversely, a lower pitch can be easier to walk on and might lower construction costs but may require more maintenance to prevent leaks and water damage.

Factors Affecting Roof Pitch Choice

Several factors influence the choice of roof pitch for a home. Climate plays a crucial role in determining the ideal roof pitch. Regions with heavy snowfall or frequent rain may benefit from steeper pitches to prevent buildup and ensure proper drainage. Architectural style also matters as certain home designs traditionally heave specific roof pitches. Additionally, local building codes and regulations can dictate the allowable range of roof pitches, impacting the final decision.

How To Find Roof Pitch With Mobile Apps & Tools

Determining your roof’s pitch can be made easy with the use of mobile apps and tools. Many smartphone applications allow you to measure the angle by simply placing your device along the roof’s slope. These apps use the phone’s sensors to give you an accurate reading in degrees. You can place your phone along the roof edge either from within the attic or from the nearest window. Some apps even allow you to hold the phone at a distance from the roof and get an accurate measurement, eliminating the need to climb up. Additionally, online calculators often require just a few simple measurements, such as the roof’s rise and run, to determine the pitch.

Knowing how to calculate roof pitch or how to calculate roof pitch degree is invaluable for various home maintenance tasks including insulation, leaking repairs and installations. By following these steps, you can safely and accurately determine the slope of your roof from the comfort of your attic.

Caution

Be careful while holding your phone along the roof edge to avoid accidentally dropping it.

FAQs

1. What Are the Different Types of Roof Pitch?

Roof pitches can vary, but common types include low slope (3:12 to 4:12), medium slope (5:12 to 7:12) and steep slope (8:12 to 12:12).

2. How do you calculate the roof pitch as a ratio?

Roof pitch is calculated as a ratio of the vertical rise to the horizontal run. It is generally noted as "X:12," where X is the number of inches the roof rises for every 12 inches it runs horizontally.

3. How Do You Calculate the Slope of a Roof?

To calculate the slope of a roof, measure the vertical rise over a 12-inch horizontal run using a level, tape measure and pencil. The level will help ensure accurate measurements, the tape measure is used to measure the vertical rise and horizontal run, and the pencil is for marking reference points during the process. Measure the vertical rise over a 12-inch horizontal run to determine the slope.

4. How to Calculate Rafters for Your Roof?

To calculate the rafters for your roof, you will need to know the pitch, run and rise of the roof. You can calculate the rafter length using the Pythagorean method, that is Raftar length = (Rise2 + Run2) Alternatively, you can input these values into a rafter length calculator for quicker results. 

5. How Does Pitch Affect the Cost of Roofing?

The pitch of a roof affects the cost because steeper roofs require more materials and labor and can be more challenging to install. On the other hand, lower slopes are generally more cost-effective to build and easier to access for maintenance.

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