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Radiator Size Calculator

Calculate the ideal radiator size for your room and enjoy maximum comfort with the perfect heat output.

Free delivery
On orders over £200
Up to 10 years warranty
On all products
Wide range of colours
*On selected products
48hr delivery
*Not on made-to-order products
Need help calculating what BTU's you need?
View Our Heat Loss Calculator
Choose The Right Radiators For Your Room

How to Calculate Radiator Sizes

You’ve found the radiator style you need, but what size is best for your room? As we know this can be a difficult question to answer, that’s precisely why we’ve designed our radiator size calculator to help.

With our radiator size calculator, you can easily figure this out and choose the right radiators every time before purchase. Since radiator sizes can vary significantly depending on the style and type of radiator you choose, it’s important to check first before placing your order.

On this page, you’ll find all the essential information you’ll need to make an informed decision. Whether purchasing electric radiators, bedroom radiators or kitchen radiators, we’ll guide you through the process to ensure you always choose the right option for your home.

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DESIGNER RADIATORS

How To Calculate Radiator Size For A Room

Radiator sizes in the UK are measured using the metric system, so you will need to ensure you measure in metres (m) or millimetres (mm). When measuring your room, ensure you have the size converted correctly as you will need to input this into the radiator size calculator.

To calculate the British Thermal Unit (BTU) output accurately and effectively for a room, you will need to grab your tape measure. Ultimately you will need to multiply the room length by its width. You should measure:

  • Room height
  • Room width
  • Room length
  • Size of the window area (length x width of your window in m²)

The reason for calculating the window dimensions is plain and simple – heat loves to escape. The bigger the window, the more chance of heat escaping. This will also differ depending on whether you have single or double-glazed windows. Single-glazed windows will lose the most heat, so your BTU will need to be higher for these.

To help make this even easier, you can use our BTU calculator to work this out effortlessly.

Once you have the room size, you can then use our calculator to work out the correct size radiator you need.

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Need help calculating what BTU's you need?
View Our Heat Loss Calculator
STELRAD

Choose From Our Range At Stelrad

At Stelrad, we have the largest range of radiator sizes in the UK, which is why our radiator size calculator is such a useful tool to help you get the correct size. Whether you decide on one of our standard-size radiators that are ever popular, or choose something more modern from our designer radiators range, we hope our calculator will assist in helping you make the right choice.

Radiator sizes and shapes at Stelrad are completely different depending on their functionality, their design and what room they belong in. Vertical Radiators have different dimensions when compared to Horizontal Radiators for example, and Bathroom Radiators such as Towel Rail Radiators will differ vastly in shape and size from one of our Column Radiators. We also have a range of compact radiators ideal for smaller rooms and spaces. Ultimately, you’ll want to find the ideal combination of style, heat output, and size to fit the room perfectly and heat it efficiently.

If you have any further questions and for all radiator FAQs, view our advice hub – we are always happy to help.

STELRAD
Home Series
Standard Steel Radiators
Standard Steel Radiators
13 Products
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Vertical Radiators
Vertical Radiators
37 Products
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Designer Radiators
Designer Radiators
33 Products
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Column Radiators
Column Radiators
10 Products
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Towel Radiators & Heated Towel Rails
Towel Radiators & Heated Towel Rails
17 Products
View All >
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RADIATOR SIZE CALCULATOR UK

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