How many roof tile vents do I need with calculator

How Many Roof Vents Do I Need?

Installing the right number of roof tile vents is important to ensure that you have adequate roof ventilation to promote air circulation through roof spaces.

At Beddoes Products, we specialise in the design and manufacture of roof tile vents, and one of the most common questions we get asked is ‘How many tile vents do you need on a roof?’. So, we put together this simple guide to help you calculate the number of roof vent tiles you will need for your roof.

Total Airflow Required

Before going into how to calculate the number of tile vents you need for your roof, you will first need to calculate the total airflow required. You can calculate the total airflow required by completing the following calculation:

Roof Length (mm) x Continuous Airflow Required (mm) = Total Airflow Required

To complete this equation you will need to know your Roof Length in millimeters (mm). You can calculate this by measuring your roof length in metres and multiplying it by 1,000. For example, a roof that is 10 Metres. You will multiply 10 by 1,000 to get 10,000 Milimetres.

The ‘Continuous Airflow Required’ is dependent on the pitch of your roof. For roofs with a pitch over 15 degrees, as most tiled roofs are, the ‘Continuous Airflow Required’ is 10 Millimeters.

Using the example figures above, here is what the equation will look like:

10,000 (Roof Length) x 10 (Continuous Airflow Required) = 100,000 (Total Airflow Required)

Total Airflow Required Calculator

To make it as easy as possible for you to calculate the required airflow required for your roof space, we have created the calculator below just for you. Simply add the length of your roof in meters and click the button.

Your Total Airflow Required:


Calculate The Number Of Vents For Your Roof

Now we know the ‘Total Airflow Required’ for our roof, we can now calculate the number of roof tile vents we will need for effective roof ventilation.

The important thing to note at this point is that the number of vents you will need is dependent on the type and design of the roof vent tile you are using. At Beddoes Products, our Roof Tile Vents vary in their ‘Ventilation Capacity’.

To make it easy for you, all of the roof tile vents have their Ventilation Capacity clearly stated in the product descriptions. This allows you to easily calculate how many roof tile vents you need before you place an order with us, by using the equation below.

Total Airflow Required ÷ Tile Ventilation Capacity = Number of Vents Required

To complete this equation all you need to do is use the figure we calculated for the ‘Total Airflow Required’ above and divide it by the ‘Tile Ventilation Capacity’ from the product description or technical data sheet. To provide you with an idea of the size of this figure, below is a table of some of our most popular roof tile vents and their ‘Tile Ventilation Capacity’.


Roof Tile Vent

Ventilation Capacity 

Plain Tile Vent


Marley Ludlow Plus Vent


Redland 49 Vent


Rosemary Roof Vent


All Other Roof Tile Vents



Calculate Number of Vents for Your Roof

Now you know your ‘Tile Ventilation Capacity’, we can now calculate the total number of roof vents required. Below we have completed an example equation using the ‘Total Airflow Required’ for our 10 metre roof length from above and some of our most popular roof tile vents’ ‘Tile Ventilation Capacity’.

Number of Vents Required:


How To Calculate Roof Tile Vent Spacing?

The final calculation we need to make is the distance required between each roof vent. This may seem obvious, but for effective roof ventilation, the roof tile vents must be positioned evenly throughout the roof to maximise the circulation of air.

This last equation is fairly simple as you can see below:

Roof Length (mm) ÷ Number of Vents = Distance Between Vents

Calculate Roof Tile Vent Spacing

Using the Roof Length (mm) from our first calculation and the figures we calculated in the previous equation for the Number of Vents you can use the calculator below to calculate the distance required between roof vents.

Roof Tile Spacing:



At Beddoes Products, we are specialists in roof ventilation and roof tile vents. Our experts create guides like these to help provide information and improve your knowledge of roof ventilation.

It is important to note that the content in this guide is for informational purposes only. We regularly check it for accuracy, however, we highly recommend that you seek professional advice and assistance from a qualified roofer or builder.

Beddoes Products will not accept liability for injury, loss or damage from the use of this content.
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