Radiators by Size

Find the right radiator size for your space—quickly and confidently. Measure your room, calculate the BTU you need, then shop radiators by height, width, and heat output. Trade Radiators has decades of experience in helping customers up and down the UK find the right sized radiator for every scenario; from compact rads for snug alcoves to high‑output options for open‑plan rooms, we’ve got sizes to fit every project.

To help you find the right size for your space, shop models from 300mm high to 1800mm wide, with BTU outputs to match.

 

What Factors Determine Which Size of Radiator to get?

When trying to get the right sized radiator, some factors you need to consider include:

• The space you have
• Your current heating system
• How easy/hard it is to heat the room
• Where the radiator is going to be located

A little research can go a long way to avoiding any radiator headaches from making a bad purchase. If you have any specific questions relating to the size of a radiator you’ve seen on our site, please get in touch directly with the team today, and we’ll be happy to help you find the perfect radiator.

 

What Sizes do Radiators Come in?

• 400mm × 400mm — compact for small bathrooms/utility rooms; expect ~1,500–2,800 BTU depending on type and material.
• 300mm × 1000mm — low‑profile under‑window runs; typically ~2,500–4,500 BTU, ideal where height is restricted.
• 400mm × 1200mm — great for corridors and kitchen walls; usually ~3,000–5,000 BTU, output varies on number of panels or columns.
• 600mm × 900mm — typical bedroom size; commonly ~3,500–5,500 BTU, sufficient for most medium rooms.
• 600mm × 1200mm — most common; outputs around ~5,000–7,500 BTU, higher outputs can be achieved for the given size by going double panel or for 4 column designs.

Note: Actual BTU for a given size varies by type, material, number of columns or panels; always match to your room’s target BTU/Watts at ΔT50 using the BTU Heating Calculator.

How to choose your radiator size

1. Measure: Record available width, height, and pipe centres for the installation area.
2. Calculate BTU: Use the BTU Heating Calculator to determine your room’s heat requirement.
3. Match outputs at ΔT50: Filter by height/width and select products whose BTU or Watts meet your requirement at ΔT50. If comparing with another site, convert their ratings using our Delta T guide. All outputs here are listed at the UK standard ΔT50.
4. Check fit: Confirm valve type, projection, and clearances from floors, skirtings, and window sills.
5. Browse sizes: Explore standard radiator sizes, including popular formats from 500 × 800 to 600 × 1200.

What Should I be Looking for When Picking a Radiator Size?

It is important to know what heat output is required from both the radiator and the room it is going in. You don’t want to buy a new designer radiator and find out it doesn’t have the right BTU for the space.

To help you know what radiator you should get, we have a handy heating calculator here on the site. You enter the dimensions of the room and what type of space it is, and we’ll give you a clear idea of the BTU you need. That will then help you know whether a radiator is suitable or not.

What Size Radiator do I get for a Room with No Central Heating?

For anyone who has converted their attic to a new bedroom or carved out a special workspace in the office, you’ll often find that these smaller spaces don’t have piping for the existing system. When that’s the case, you’ll want to look at getting an electric radiator sized to your room’s BTU/W; same sizing rules apply.. They come in the same makes and sizes but have an electric element inside that helps you plug in and have the radiator on when you need it. You can find out more at our electric heating section.