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Radiator Size Calculator

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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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How to Calculate Radiator Sizes
How to calculate radiator size for a room

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.

What size radiator
are you looking for?

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.

Single/Flat Panel or Double Panel Radiators
Single/Flat Panel or Double Panel Radiators
These radiators are some of the most commonly used for central heating systems. Central heating radiators are available in two primary configurations: a slim single panel that hugs the wall closely or double panels separated by a gap with convection fins, which enhances their heat output.
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Horizontal or Vertical Radiators
Horizontal or Vertical Radiators
Horizontal radiators have a wider width than height and are often positioned beneath windows. Vertical radiators are characterised by their greater height compared to width, making them excellent choices for conserving space. Additionally, due to their heightened visibility, vertical radiators frequently feature a wider array of decorative designs to choose from.
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Column Radiators
Column Radiators
Column radiators consist of a vertical alignment of metal tubes connected at both the top and bottom ends. They are available in both horizontal and vertical designs, typically offering a more classic aesthetic compared to flat panel radiators that can add character to a room.
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Towel Radiators
Towel Radiators
Towel radiators stand out as the ideal choice for bathroom heating solutions. Consisting of a sequence of horizontally arranged tubes in a ladder-style pattern, they excel at efficiently warming towels. In addition to their practicality, towel radiators also enhance bathroom aesthetics, adding a touch of decorative flair when compared to standard flat panel radiators.
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Designer Radiators
Designer Radiators
Designer radiators, frequently referred to as modern or contemporary radiators, present a fusion of functionality and style. These radiators deliver warmth while serving as visually striking focal points in any home. They are available in a variety of formats, including horizontal, vertical, column, and towel radiators, all with stylish designs and an array of diverse finishes to suit your décor.
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Space-Saving Radiators
Space-Saving Radiators
Space-saving radiators make the most of compact spaces while simultaneously contributing to the overall room design. You could choose a compact single flat panel radiator that snugly hugs the wall, ensuring it doesn't intrude significantly into the room, or space-efficient vertical radiators that are an excellent choice for areas where furniture or kitchen cabinets must be considered.
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FAQs

RADIATOR SIZE CALCULATOR UK

What size radiator do I need?

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Using our radiator size calculator will help you decide what dimensions your new radiator should be to accommodate your space and how to calculate the radiator size for your room. Using our radiator sizing guide is great for physical measurements, but another useful tool to help you calculate how much heat output is appropriate for your room is our BTU Calculator. This heat loss calculator will work alongside our radiator size calculator for UK radiators, helping create a radiator size chart that will direct you to which model of radiator is most suitable for your room.

What size radiator do I need for my room?

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The size of radiator you need for your room will be dependent on its dimensions. If you are replacing an existing radiator, for example, and are wondering how to calculate radiator size for a room, follow these 4 simple steps:

  • Measure the height of where the radiator will be placed.
  • Measure how wide you need your radiator to be.
  • Measure the pipe centres (from the centre of the left-hand pipe inlet to the centre of the right)
  • Measure the wall-to-pipe centres (from the centre of the pipe inlet to the wall)

You can then use our radiator size calculator to input the measurements to see which of our ranges will be suitable as a replacement.

Do radiators come in standard sizes?

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Radiator sizes are not consistent over different models, due to their varying dimensions. For example, a Vertical Radiator will be much taller than it is wide when compared to a standard horizontal radiator. Using our radiator size tool and BTU calculator can ensure you choose the right dimensions for your room, rather than choosing the same size for every room which may not be as energy efficient.

What are standard radiator sizes?

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We have a range of radiator sizes at Stelrad that are suitable for many different room requirements. For example, our Classic Compact radiators range in height between 300mm – 700mm and widths of 400mm – 2400 mm, whereas our Compact Vertical is 1800mm in height with a choice of widths between 400mm – 600mm.

As you will find when browsing our range, “Standard” doesn’t mean one-size at Stelrad. We have many options because every room is different and every property is differently sized, helping you choose the right size for your needs. You’ll see full details of the available sizes to suit your needs by using our radiator size calculator.

What is BTU?

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British Thermal Unit (BTU) is the traditional unit of heat to measure the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. As this can be quite complex, using a BTU calculator makes working this out easy. Put simply, the higher the BTU output of a radiator, the more heat it can produce. The size, shape, and material used for the radiator will all determine its BTU output.

To know the number of BTUs required per radiator, this will depend on the number of radiators in the room. Divide the total BTU requirement by the number of radiators. This will calculate the average BTUs required for each radiator. You can use our BTU calculator to follow a step-by-step guide to calculate heat loss in your home for any room. This will help you choose the right size radiator with your taken room measurements, as well as details about the walls, floor, glazing etc. it has.

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