How to calculate a roof pitch?

Understanding how to calculate a roof pitch is of vital importance for both homeowners and builders, as its effects include its ability to shed water efficiently, aesthetic appeal, and overall durability of a roof. Here we outline what roof pitch is, its calculation tools required, and an easy four-step method of finding its pitch on any given roof!

What Is Roof Pitch?

Roof pitch refers to the steepness or slope of a roof and is commonly expressed as an elevation ratio such as 4:12. This ratio shows how a roof rises 4 inches for every 12 inches horizontal run – or it could also be expressed using degrees or percentages. Knowing your pitch can significantly impact a roof’s design, drainage capacity, and material selection process.

Tools and Materials Needed

To calculate the roof pitch, you will need:

• Measuring tape
• Level
• Calculator
• Pencil
• Paper

However digital tools or apps specifically for roofing pitch calculations may make the task quicker and more accurate!

Steps for Calculating Roof Pitch

Step 1: Measure Horizontal Run 

The horizontal run measures the distance from the edge of your roof to directly under its peak or ridge, as measured with your measuring tape and level. Ensure the tape remains straight while paralleling with the ground for accurate results.

Step Two: Measure Vertical Rise 

To measure vertical rise, place one end of your level against the roof’s edge to make sure it remains horizontal before taking measurements from its base to the peak of the roof. To accomplish this task, set out two levels side-by-side between where they meet at either edge, measuring from the bottom level up until the peak is reached.

Step 3: Calculating Pitch Ratio 

The pitch ratio can be calculated by dividing vertical rise by horizontal run; for instance, if your rise measures 6 inches while your run measures 12 inches then 6:12 could be your pitch ratio; which can also be simplified down to 1:2 if necessary.

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Step 4: Convert the Pitch Ratio to Degrees or Percentage

To convert the pitch ratio to degrees, use the formula:

Degrees: Degrees = tan^(-1) (rise/run)

Percentage: Percentage = (rise/run) * 100

Example 1

Pitch ratio: 8:12

Converting to degrees:

Degrees = tan^(-1) (8/12) = tan^(-1) (0.6667) ≈ 33.69°

Converting to percentage:

Percentage = (8/12) * 100 ≈ 66.67%

Example 2

Pitch ratio: 5:12

Converting to degrees:

Degrees = tan^(-1) (5/12) = tan^(-1) (0.4167) ≈ 22.62°

Converting to percentage:

Percentage = (5/12) * 100 ≈ 41.67%

The Bottom Line

Knowing how to calculate a roof pitch accurately for any roofing project is of critical importance in all stages, from aesthetic considerations to functionality and longevity considerations. By following the steps outlined above, you can accurately ascertain your roof’s pitch. A2Z Roofing offers professional assistance for every need imaginable – visit our website for more details or consultation requests!