How to Calculate Roof Pitch?(3 Easy Steps)

John McEvoy
May 2, 2023

Calculating roof pitch is a critical aspect of the roofing process. It affects your home's aesthetics and determines its ability to withstand various weather conditions. This comprehensive guide will explore how to calculate roof pitch in various ways, helping you make informed decisions regarding your roofing needs.

Whether you are a homeowner or a professional roofer, HP Roofing, a trusted Irish roofing company, is here to help you every step of the way.

What is Roof Pitch?

Roof pitch refers to the steepness or slope of a roof, which is expressed as a ratio of the vertical rise to the horizontal span. A higher pitch indicates a steeper roof, while a lower pitch denotes a more gradual slope. Understanding roof pitch is essential for various aspects of your roofing project, including material selection, drainage, insulation, and aesthetics.

How to Measure Roof Pitch?

To calculate the roof pitch, you need to determine the rise and run of your roof. Here's how:

Step 1: Measure the horizontal distance (run)

From the roof's edge, measure the horizontal distance (in inches) to a point directly below the roof's highest point. This measurement is called the run.

Step 2: Measure the vertical distance (rise)

Next, measure the vertical distance (in inches) from the roof's highest point to the same point used for the run measurement. This measurement is called the rise.

Step 3: Calculate the roof pitch

Now, divide the rise by the run, and multiply the result by 12 to express the roof pitch as a ratio of inches of rise per foot of run (e.g., 4/12, 6/12).

How to Determine Roof Pitch in Degrees?

Calculating roof pitch in degrees is a precise method that requires a few simple tools and a basic understanding of trigonometry. Follow these steps to measure roof pitch in degrees:

  • Access the roof safely and measure the horizontal run (in inches).
  • Measure the vertical rise (in inches).
  • Use a scientific calculator to find the angle in degrees. Use the formula: Angle = arctan (rise/run). Don't forget to convert the result from radians to degrees if needed.

How to Determine Roof Pitch as a Ratio?

Calculating roof pitch as a ratio is a simpler method often used in the construction industry. To calculate roof pitch as a ratio, follow these steps:

  • Measure the horizontal run (in feet).
  • Measure the vertical rise (in inches).
  • Determine the ratio by dividing the rise by the run and multiplying by 12. The resulting ratio is typically expressed as X/12, where X is the rise for every 12 inches of run.

How to Calculate Roof Pitch Using a Roof Pitch Calculator?

Roof pitch calculators are online tools that simplify the process of calculating roof pitch. Simply enter the required measurements, and the calculator will give you the pitch in degrees or as a ratio. Here are some steps to follow when using a roof pitch calculator:

  • Measure your roof's horizontal run and vertical rise, as described in the previous sections.
  • Visit a reputable online roof pitch calculator.
  • Input the measurements you have taken.
  • Review the calculated pitch in degrees or as a ratio.

How to Determine Roof Pitch Using an Angle Finder?

If you have an angle finder, you can determine the roof pitch without measuring the rise and run. Place the angle finder on the roof slope, ensuring its level, and read the angle. Convert the angle to a roof pitch using the following formula:

Roof Pitch = tan(angle) x 12

For example, if the angle is 30 degrees, the roof pitch is:

Roof Pitch = tan(30) x 12 ≈ 6.93/12

Understanding Roof Pitch Categories

Roof pitches can be classified into three main categories:

Low Slope

Roof pitches between 1/12 and 3/12 are often used for commercial buildings and modern residential designs. These roofs require special attention to drainage and waterproofing.

Medium Slope

Roof pitches between 4/12 and 6/12 are commonly found in residential homes. These roofs provide a balance between drainage efficiency and architectural aesthetics.

Steep Slope

Roof pitches over 6/12 are often used for traditional and historic architectural styles. These roofs offer excellent drainage and create additional attic space, but they may be challenging to walk on and maintain.

Choosing the Right Roof Pitch for Your Project

Selecting the appropriate roof pitch for your project depends on several factors, including:

Local climate

A steeper roof pitch may be necessary to prevent snow and water accumulation in areas with heavy snow or rain.

Architectural style

The roof pitch should complement the overall design of your home and blend seamlessly with the surrounding neighbourhood.


Steeper roof pitches can create additional living or storage space in the attic.


Higher roof pitches may require more materials and labour, resulting in higher costs. Ensure you consider your budget when choosing a roof pitch.

Local building regulations

Check with your local building authorities for any restrictions or requirements regarding roof pitch in your area.

Ready to Calculate Roof Pitch with HP Roofing?

Now that you know how to calculate roof pitch, you can make informed decisions about your roofing needs. Whether planning a new build or renovating an existing roof, HP Roofing is here to help. Our team of experts can assist with all aspects of your roofing project, from calculating roof pitch to selecting the right materials and providing professional installation.

Contact us today!

HP Roofing is a team of residential & commercial roofing contractors and solar panel installation experts in Dublin. We offer a wide range of services, from roof repairs and replacements to solar PV installations and maintenance, with quality beyond expectations.
Call HP Roofing 01 453 3366

Frequently Asked Questions

What is the standard pitch for a roof?

The standard pitch for a roof varies depending on the style of the house and local weather conditions. Generally, a pitch of 4/12 to 9/12 is standard for most residential roofs.

What is the formula for pitch angle?

The pitch angle formula is Angle = arctan (rise/run). Don't forget to convert the result from radians to degrees if needed.

What is a 4/12 roof pitch?

A 4/12 roof pitch indicates the roof rises 4 inches vertically for every 12 inches of horizontal run. This relatively low slope is suitable for various architectural styles and climates.

What roof pitch is walkable?

Roof pitches up to 6/12 are generally considered walkable, though caution should still be exercised. Steeper pitches may require additional safety equipment or professional assistance when working on the roof.

What is the smallest pitch of a roof?

The smallest pitch of a roof is typically 1/12, considered a low-slope roof. Roofs with this pitch require specific materials and installation techniques to ensure proper drainage and prevent water infiltration.

What roof pitch are 30 degrees?

A roof pitch of 30 degrees is equivalent to a 7/12 pitch. This means the roof rises 7 inches vertically for every 12 inches horizontal run. This pitch is common in various architectural styles and balances aesthetics and functionality well.

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*FYI, parts of this blog post were drafted by artificial technlogy. But rest assured, it's been thoroughly researched, edited, reviewed and me & my team.
Founder @ HPRoofing

The founder of HP Roofing, with years of industry experience, providing top-notch roofing and solar panel services for residential and commercial properties in Dublin, delivering high-quality and customised solutions that combine both aesthetic appeal and durable functionality.