
Reliable, space‑saving radiators designed for everyday home heating.

Slim single‑panel radiators ideal for smaller rooms.

Sleek, smooth‑front radiators for a modern, minimalist look.

Two‑panel radiators offering increased heat output.

Radiators featuring subtle linear detailing for added texture and style.

Enhanced double‑panel radiators with extra convection fins.

Eco‑focused radiator made with low-carbon emission XCarb steel

High‑output triple‑panel radiators for larger or colder spaces.

Fast‑heating radiators that circulate warm air efficiently.

Radiators with a clean, flat top grille for a tidy finish.
Traditional column styling powered by efficient electric heating.
Multicolumn radiator range demonstrates the perfect combination of style and function.
Heavyweight cast‑iron radiators that retain heat for long‑lasting warmth.

Heritage‑inspired radiators with classic, period charm.

Classic horizontal column radiators for traditional interiors.

Tall column radiators that blend vintage style with modern performance.

Column radiators available in bold, custom colour finishes.

Triple‑column radiators offering balanced heat and timeless design.

Versatile four‑column radiators combining style and strong heat output.

Deep, multi‑column radiators delivering powerful heat output.
Premium electric radiators that pair standout design with efficiency.

Tall radiators that save space while delivering strong heat.
Radiators engineered to deliver maximum heat performance.

Clean, neutral white radiators that suit any décor.

Ultra‑premium Scandinavian radiators known for minimalist design and quality.

Radiators available in a wide range of bespoke colour options.
Contemporary grey radiators for a modern, architectural look.
Polished chrome radiators for a sleek, reflective finish.

Sleek, smooth‑front radiators for a modern, minimalist look.

Radiators featuring subtle linear detailing for added texture and style.

Radiators with tubular bars for efficient heat and striking design.
Space‑saving electric radiators designed for vertical installation.

Sleek, smooth‑front radiators for a modern, minimalist look.

Featuring subtle linear detailing for added texture and style.

Radiators with tubular bars for efficient heat and striking design.

Tall column radiators that combine classic styling with strong, space‑saving heat output.
Purpose‑built radiators engineered for unique spaces or specialist heating needs.
Low‑surface‑temperature radiators ideal for schools, care settings, and safe environments.

Featuring subtle linear detailing for added texture and style.







































Calculate the ideal radiator size for your room and enjoy maximum comfort with the perfect heat output.
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.
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:
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.
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.
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.
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:
You can then use our radiator size calculator to input the measurements to see which of our ranges will be suitable as a replacement.
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.
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.
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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