How to Figure Out the Angle of a Roof?

John McEvoy
January 17, 2024

Do you need to install a new roof or replace an old one? If so, you might be wondering how to figure out the angle of a roof. The angle of a roof, also known as the pitch or slope, is an important factor that affects the design, performance, and durability of your roof. Knowing the angle of your roof can help you choose the right roofing materials, calculate the roof area, and estimate the cost of your project.

But how do you measure the angle of a roof? What tools and methods do you need? And what are the benefits of having a certain roof angle? This blog post will answer all these questions and more. By the end of this blog post, you will have a very in-depth understanding of how to figure out the angle of a roof.

What is the Angle of a Roof?

The angle of a roof is the measure of how steep or flat your roof is. It is usually expressed as a ratio of the vertical rise to the horizontal run or as a degree of inclination. For example, a roof that rises 4 inches for every 12 inches of horizontal distance has a 4:12 pitch, or an angle of 18.43 degrees.

What are the Types of Roof Angles?

The angle of a roof can vary depending on the style, design, and purpose of your roof. Some common types of roof angles are:

Flat roof

A roof that has no slope or a very low slope (less than 10 degrees). Flat roofs are easy to install and maintain, but they are subjected to water damage, leaks, and mould growth. They are also less energy efficient and cause more wind damage than sloped roofs.

Low-slope roof

A roof that has a slope between 10 and 20 degrees. Low-slope roofs are common in commercial and industrial buildings, as they allow for more usable space and easier access to equipment and utilities. However, they also require more frequent inspection and maintenance. They also have lower aesthetic appeal and less ventilation than steeper roofs.

Medium-slope roof

A roof that has a slope between 20 and 40 degrees. Medium-slope roofs are the most popular choice for residential buildings, as they offer a balance between performance and appearance. They are suitable for most climates and roofing materials, and they provide good drainage, insulation, and ventilation. They also have a moderate cost and maintenance requirement, and they can accommodate various architectural features, such as dormers, skylights, and chimneys.

High-slope roof

A roof that has a slope greater than 40 degrees. High-slope roofs are often seen in traditional and historical buildings, such as cottages, barns, and churches. They have a high aesthetic appeal and distinctive character, and they can enhance the appeal and value of your property. However, they also have a high installation and maintenance cost, and they require special roofing materials and techniques.

How to Figure Out the Angle of a Roof Using Different Methods

There are several ways to figure out the angle of a roof, depending on the tools and information you have available. This section will discuss four of the most common methods: using a level, using a protractor, using a calculator, and using an online tool.

Using a Level

This method involves using a level and a tape measure to find the rise and the run of your roof, and then dividing them to get the pitch. To convert the pitch to an angle, you need to find the inverse tangent of the pitch. This method is simple, cheap, and accurate, but it can be dangerous and require assistance.

Using a Protractor

This method involves using a protractor and a plumb bob to find the vertical direction and measure the angle of your roof. You need to hang the plumb bob from the ridge or the peak of your roof, and then place the protractor on the roof surface and read the angle. This method is accurate and precise, but it can also be dangerous and inconvenient.

Using a Calculator

This method involves using a calculator or an online tool to find the angle of your roof based on the dimensions of your roof, such as its length, width, and height. You need to find the area, the volume, and the slope of your roof, and then find the inverse sine of the slope. This method is easy and fast, but it can be inaccurate and require estimation.

Using an Online Tool

This method involves using an online tool to find the angle of your roof based on the information you have, such as the pitch, the rise, the run, the area, the volume, or the slope. You need to enter the information you have, and the tool will calculate the angle for you. This method is easy and fast, but it can be unreliable and require internet access.

Why is the Angle of a Roof Important?

The angle of a roof is not just a matter of preference or style. It also has a significant impact on the performance, durability, and efficiency of your roof. Here are some of the reasons why the angle of a roof is important:


The angle of a roof affects how well water and debris can drain off your roof. A steeper roof has better drainage than a flatter roof, as it allows water to flow faster and prevents pooling. This reduces the risk of leaks, rot, mould, and structural damage.


The angle of a roof affects how well your roof can insulate your home from heat and cold. A steeper roof has more air space between the roof surface and the ceiling, which acts as a buffer and reduces heat transfer. This can help you save energy and lower your heating and cooling bills.


The angle of a roof affects how well your roof can ventilate your home and prevent moisture and air quality problems. A steeper roof has more air circulation than a flatter roof, as it creates a natural draft that draws fresh air in and pushes stale air out. This can help you prevent mould, mildew, and odours and improve your indoor comfort and health.


The angle of a roof affects how your roof looks and complements your home’s architecture and design. A steeper roof has more visual appeal and character than a flatter roof, as it creates a more dynamic and dramatic shape. It can also enhance the appeal and value of your property, especially if you choose a roofing material that matches your home’s style and colour scheme.

How to Choose the Right Angle for Your Roof

There are many factors to consider when choosing the right angle for your roof. There is no one-size-fits-all answer, as different roof angles have different pros and cons.

However, here are some general tips to help you make an informed decision:

Consider the Climate and Weather Conditions

The angle of your roof affects how well it can withstand rain, snow, wind, and heat. A steeper roof has better drainage, insulation, and ventilation, but it also requires more flashing and sealing. A flatter roof has lower heat gain, but it also requires more inspection and repair.

Consider the Style and Design of Your Home

The angle of your roof affects how your roof looks and matches your home’s architecture and design. A steeper roof has more visual appeal and character, but it also requires more maintenance and cleaning. A flatter roof has a sleek and simple look, but it also has lower aesthetic appeal and less ventilation.

Consider the Cost and Maintenance of Your Roof

The angle of your roof affects how much money and time you need to spend on your roof installation and maintenance. A steeper roof requires more roofing material and labour, but it also has less water damage and leaks. A flatter roof requires less roofing material and labour, but it also has more debris, snow, and ice accumulation.

Consider the Functionality and Usability of Your Roof

The angle of your roof affects how much space and access you have on your roof. A steeper roof has less usable space and more safety risks, but it also has more air circulation and weather resistance. A flatter roof has more usable space and flexibility, but it also has more safety and security risks.


To wrap up, figuring out the angle of your roof is really important for a good roof job. It helps you pick the right stuff for your roof and understand how much it might cost. This blog post showed you easy ways to measure your roof's angle and why it matters. If you need help with your roof and want to make sure it's done right, HP Roofing is here to help.

They know all about roofs and can make sure yours is perfect for your home. Contact HP Roofing today to get started on optimising your roof for longevity and performance.

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

How do I calculate the roof pitch from inside my attic?

You can measure the roof pitch from the attic by using a level to measure 12 inches from a rafter, and then measure vertically from the 12-inch mark to the roof. The rise over this 12-inch run is your roof's pitch.

What are the key terms for measuring roof pitch?

Important terms include "rise" (the vertical distance from one point to the highest point of the roof), "run" (the horizontal distance from the peak of the roof to the exterior wall), and "slope" (the incline of the roof represented as inches of vertical rise per foot of horizontal run).

How do you use a roof pitch chart?

A roof pitch chart visually represents the slope of a roof given its pitch. The pitch is often expressed as a ratio of vertical rise to horizontal run, such as X in 12, where X is the number of inches of rise for every 12 inches of run.

What is the best pitch for a roof?

The best roof pitch depends on the style of the roof, the roofing material, and climate concerns. Medium- or high-roof pitches are often recommended for areas with heavy snow, rain, or wind.

What is the minimum roof pitch for snow?

The minimum roof pitch for shedding snow is around 30°, corresponding to a 6:12 or 7:12 slope. However, this can vary based on factors like roofing material and weather conditions.

How do you measure the pitch of the roof?

To measure roof pitch directly on the roof, measure 1-foot up from the base for the run, then use a level at this point and measure from the bottom of the level to the top of the roof for the rise.

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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.