Not sure what size radiator you need? This simple guide explains how to choose the right radiator based on your pipe centres, room size, and heat output requirements.
Step 1 – Measure Pipe Centres (For Replacement Radiators)
If you are replacing an existing radiator:
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Measure the distance between the centre of your pipes
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This measurement determines the radiator width
→ Most radiators have pipe centres approximately 45mm less than the total width
(e.g. a 400mm radiator typically has a 355mm pipe centre)
⚠️ Always check the product description as some models may vary.
Step 2 – Choose the Right Radiator Size
Radiator size depends on:
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Wall space available
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Room size
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Heat output required
→ Taller radiators provide more heat output
→ Wider radiators cover more wall space
Vertical radiators are ideal for compact rooms where wall width is limited.
Step 3 – Understand Heat Output (BTU)
BTU (British Thermal Unit) measures how much heat a radiator produces.
→ As a general guide:
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Small bathroom: 1000–2000 BTU
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Bedroom: 2000–4000 BTU
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Living room: 4000–8000+ BTU
→ Larger or poorly insulated rooms will require higher BTU radiators.
Why Choosing the Right Size Matters
Selecting the wrong radiator size can lead to:
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Rooms not heating properly
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Increased energy bills
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Extra strain on your boiler
- Possibly forcing you to return a towel rail
Tips for Choosing the Right Radiator
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Always check the BTU rating before buying
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Choose slightly higher output for colder rooms
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Consider vertical radiators for small spaces
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Ensure pipe centres match your existing setup
Find the Right Radiator
→ Browse our range here:
Central Heating Radiators
→ Explore towel radiators:
Towel Radiators
Need Help?
If you're unsure what size radiator you need, our team is happy to help.
Contact us via live chat, email, or phone for expert advice.
