How to Calculate Roof Pitch Step-by-Step

A roof pitch refers to the slope of the roof, determining how steep or flat it is. This seemingly simple factor holds great significance in regards to construction and design. 

The pitch plays a vital role in how water drains off the roof, impacting its longevity and the materials you can use. It’s not just about aesthetics; it’s about the very foundation of your home’s protection against the elements.

Read on to find out exactly how to calculate your roof pitch, step-by-step. No need for complicated equations or confusion. 

How to Calculate Roof Pitch: What You’ll Need

To work out the pitch of a roof, you’ll need some basic measurements and tools as follows:

• A standard measuring tape to measure the dimensions of the roof.
• A spirit level is used to ensure that your measurements are accurate and the surface is even.
• A pencil and paper to jot down your measurements and perform calculations.
• Calculator to help make any calculations easier.
• An online pitch calculation tool or to simplify the calculation process (if preferred.)
• App to work out a pitch from a photo (even simpler.)

Steps for Manually Measuring the Roof Pitch

1. Getting the measurements needed to calculate the pitch
   1. Measure the vertical height from the top of the roof to the start of the structure wall. This is called the rise.
   2. Measure the horizontal distance that spans between the highest point of the roof and the wall. This is called the run.

These measurements are needed to calculate the pitch manually and can also be input into an online pitch calculation tool.

2. To calculate the pitch:
   1.  Divide the rise by the run. This gives the tangent of the roof. (rise ÷ run = tangent) Use the arctan function on a calculator (tan-1), or type arctan (*tangent*) into a search engine like Google or Bing.
   2. Multiply whatever the result is by 180/π and this will give the pitch of the roof. Roof Pitch = [arctan(tangent) (Rise ÷ Run)]*180/π

How to Calculate Roof Pitch: Using an Online Calculation Tool or App to Measure

There are a number of online pitch calculation tools that can remove the need to do all of the above calculations although you will still need the rise and run measurements. An example of this is the Omni roof pitch calculator 

Online Apps are also available which can work out a pitch from a photo although they can sometimes get this wrong if the camera angle or light isn’t quite right.

The phone case also needs to be flat at the back and if it’s not it can throw out the pitch measurement. This may sound obvious but some new phone cases have a raised area around the camera to give extra protection. Phone Apps include:- 

1. ImageMeter – photo measure, 
2. Ruler – Bubble Level – Angle Meter
3.  Simple Inclinometer

Keeping safe

Getting precise roof pitch angle measurements may involve working at height. Care needs to be taken to ensure the roof and the person remain safe and do not come to any harm.

This is the case whether the person is going up on the roof outside or taking measurements inside in a loft space. If unsure, it is always advisable to seek help from a professional.

What is Roof Pitch? 

A roof pitch is a numerical measure that expresses the steepness or slope of a roof.

The steeper the slope the higher the roof pitch is. Roof pitches are significant in construction and design for various reasons, including drainage, aesthetic considerations, and the types of roofing materials that can be used.

Different roof pitches are associated with different architectural styles and can impact the overall appearance and functionality of a building.

In the specific context of roofing, pitch is commonly used to describe the steepness of a roof, often expressed as a ratio, while slope may be used interchangeably or to describe the angle of inclination in degrees.

In a broader construction sense, slope can also refer to the inclination of any surface, not limited to roofs.

What is a Roof Pitch Ratio?

The roof pitch ratio is a numerical expression that represents the steepness or slope of a roof.

It is typically presented as a ratio of vertical rise to horizontal run and is expressed in the form of “X:12,” where X is the vertical rise, and 12 is the horizontal run.

A higher first number indicates a steeper pitch, while a lower first number indicates a shallower pitch.

For example: A roof pitch of 6:12 means that for every 12 units of horizontal distance, the roof rises by 6 units vertically.

A roof pitch of 8:12 means that for every 12 units of horizontal distance, the roof rises by 8 units vertically.

How to Calculate Roof Pitch: Tips and Tricks

Calculating roof pitch is a fundamental step in construction and roofing projects. Here are some tips and tricks to help you with roof pitch calculations:

1. A quality measuring tape and spirit level are essential tools for accurate measurements.
2. Ensure that you follow proper safety measures, especially if you are climbing onto the roof. Use a stable ladder and take precautions to prevent accidents.
3. Understand roof pitch terminology and the difference between run, rise, pitch and slope.
4. Use an online pitch calculator to avoid having to do any calculations by hand. To do this you will need to input the rise and run numbers.
5. Calculate the roof pitch using an App on your smartphone.
6. If available, refer to building plans or blueprints, as they often include information about the roof pitch.
7. Ensure you comply with any local building planning requirements. These may specify minimum pitch requirements and roofing materials that can be used.
8. Consider different roofing materials and any specific pitch requirements they may have. Consult the manufacturer’s guidelines to ensure proper installation.
9. Accuracy is crucial so it’s important to double check any measurements and calculations to avoid errors that could lead to issues during construction.
10. If you’re unsure about your calculations or getting the measurements from your roof, seek help from a roofing professional who has the experience and expertise to ensure accurate measurements.

Safety and precision are top priorities when working on roof pitch calculations. If in doubt, it’s always wise to consult with a roofing professional or structural engineer.

The Importance of Knowing Your Roof Pitch

Knowing your roof pitch is crucial for various reasons, and it plays a significant role in the construction, maintenance, and functionality of your roof.

Here are some factors highlighting the importance of knowing your roof pitch:

Water Drainage

Roof pitch directly affects water drainage. Steeper pitches allow water to run off more efficiently, reducing the risk of water pooling and potential leaks. Proper drainage helps prevent water damage to the roof and the underlying structure.

Selection of Roofing Materials

Different roofing materials are designed for specific pitch ranges. Knowing your roof pitch is essential for choosing the right roofing materials that are compatible with the slope. This ensures proper installation and longevity of the roof.

Aesthetic Considerations

Roof pitch contributes to the overall aesthetic appeal of a building. Different architectural styles are associated with specific roof pitches. Knowing and maintaining the intended pitch can preserve the architectural integrity and visual harmony of the structure.

Snow Load & Weight Distribution 

In areas with a risk of heavy snowfall, the pitch of the roof will influence how snow accumulates and sheds. Steeper pitches are less likely to retain large amounts of snow, reducing the risk of structural damage due to excessive snow load.

Attic Space & Ventilation

The pitch of the roof affects the usable space and ventilation in the attic. Steeper pitches may provide more attic space, while shallower pitches might limit storage options. Proper attic ventilation is essential for preventing moisture buildup and extending the life of the roof.

Local Building and Planning Regulations 

Building and planning regulations may apply, and these may specify minimum pitch requirements. Complying with these regulations is essential to ensure the safety and compliance of your roof structure.

Roof Repair & Maintenance

Knowing the pitch is essential for safely navigating and working on the roof when planning roof repairs or maintenance. Different pitches may require specific safety measures or equipment.

Energy Efficiency

Roof pitch can impact energy efficiency. Steeper roofs may provide better natural ventilation, reducing the need for mechanical cooling. Additionally, solar panels are often installed at specific pitches to maximise energy generation.

Resale Value

Prospective homebuyers may consider the roof pitch when evaluating a property. A well-maintained roof with an appropriate pitch can sometimes enhance a home’s resale value.

Architectural Compatibility

Some architectural designs and styles require specific roof pitches for visual harmony. Knowing and maintaining the correct pitch is essential to preserve the intended design and aesthetics.

Summary Of Calculating Roof Pitch

Whether you have a flat roof, a standing seam, or any other kind of roof, knowing your roof pitch is essential for functional, structural, and aesthetic reasons. It ensures proper water drainage, facilitates the selection of appropriate materials, and contributes to the overall integrity and longevity of your roof structure.

1. Gather necessary tools- a standard measuring tape, spirit level, pencil and paper and a calculator.
2. Measure the vertical height from the top of the roof to the start of the structure wall (the rise).
3. Measure the horizontal distance that spans between the highest point of the roof and the wall (the run).
4. Now get ready to do some calculations by hand or using a calculator.
   1. Divide the rise by the run. This gives the tangent of the roof. (rise ÷ run = tangent) Use the arctan function on a calculator (tan-1), or type arctan (*tangent*) into a search engine like Google or Bing.
   2. Multiply whatever the result is by 180/π, and this will give the pitch of the roof. Roof Pitch = [arctan(tangent) (Rise ÷ Run)]*180/π
5. Double-check any measurements and calculations to ensure accuracy. Mistakes in measurements can lead to errors in the pitch calculations. 
6. If you need to work at height or on the roof to obtain measurements, always prioritise safety, ensuring you have the appropriate safety equipment, work with a partner if possible and avoid working in adverse weather conditions. 
7. Rather than doing a manual measurement, if preferred an online pitch calculation tool can be used to simplify the calculation process.

If you have any questions regarding how to calculate roof pitch or have a specific building project that you’d like to talk through with one of our technical experts, please get in touch with us here.