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How to measure a radiator

Man leaning over to look at radiator -how to measure a radiator

You’ll need to know how to measure a radiator when it comes to replacing it. It’s super important to get the size exactly right so you can make sure your replacement radiator fits your plumbing and your space perfectly. You may also want to measure your radiator so you can fit a radiator cover – you can read more about this in our Do radiator covers block heat? article.

In this guide, we’ll be talking about how to get your measurements right for central heating radiators that are plumbed into your water supply and boiler, rather than electric radiators or oil-filled heaters.

Table of contents

  1. Should I match my old radiator?
  2. How to measure your radiator for replacement
  3. FAQs
  4. Repair your home with confidence

Should I match my old radiator?

It’s totally up to you! If you’re choosing a similar size and shape radiator to your old one, replacing like for like, you’ll want to match your measurements exactly when you shop online or in person. If you want a different look or function – for instance, you want to replace a bathroom radiator with a heated towel rail, or go for a more traditional or modern look – you’ll need to alter your plumbing so that a radiator with different dimensions can be plumbed in.

How to measure your radiator for replacement

We’ll make sure you’ve got everything you need to correctly measure your radiator, so you can install a replacement without a hitch. Remember to record all your measurements in millimetres; then you can match your measurements to the ones available in shops and online.

The four vital measurements of your radiator:

  1. Measure radiator height (mm)
  2. Measure radiator width (mm)
  3. Measure left pipe centre to right pipe centre (mm)
  4. Measure the wall to pipe centres (mm)

Follow our step-by-step instructions to get these four measurements (along with some handy extra tips) and you’ll have everything you need to shop around for your new radiator.

What you’ll need:
– A tape measure
– Pad and pen (or make a note on your smartphone)

  1. Measure radiator height
    It’s easy to measure your radiator height – just take your tape measure from the lowest point of your radiator to the highest. If it’s a very tall radiator you may need a step-ladder and someone to hold it for you.Measure radiator height
  2. Measure radiator width
    To calculate the width of your current radiator, start your tape measure on the furthest point on the left, to the furthest point on the right of your radiator. Again, if it’s a wide radiator, you may need someone to help you.
  3. Measure pipe centres
    Measuring your radiator pipe centres means measuring the distance between the two pipes feeding into and out of your radiator. You need to measure from the centre of one of the pipes to the centre of the other so that you can choose a replacement radiator with the exact same pipe centre measurement (and avoid having to do any plumbing work to rearrange your pipes). How to measure your pipe centres: Place the start of the tape measure from the centre of the left-hand pipe inlet to the centre of the right-hand pipe inlet. When you’re shopping online for a new radiator, the website will list the pipe centre measurements on the product page to help make choosing a matching radiator easy.radiator with measurements -How to measure your pipe centres
  4. Measure wall surface to pipe centres
    For this measurement, you need to start your measuring tape at the wall and measure the short distance from the wall to the centre of the pipes in millimetres. The figure you end up with will help you determine how far away from the wall your pipework is, which is useful if you don’t want to alter any plumbing when replacing a radiator.

Extra tips

You’ll also find that it helps to record a couple of extra measurements:

Wall distance

Wall distance is the gap between your wall and the radiator’s surface (the one that faces the wall). This helps you calculate the amount of space behind your radiator when it’s installed. You can take this measurement either on top of the radiator or at the side.

Wall to face

How far does your radiator protrude into the room? If you’re short on space, you may want to consider getting this measurement – from the wall to the front of your radiator – and seeing if you can get a slimline radiator.

Got your measurements? Now go online

Now you’ve got your measurements, it’s time to shop around for a new radiator. Armed with your exact measurements, you can cut out the guesswork and search only for radiators with the correct dimensions. No fear of having to alter pipework, unless of course, you’re going for something completely different.


How do I know what size radiator I need?

If you’re replacing your radiator like for like, you must take the exact measurements of your old radiator and make sure your replacement radiator matches those measurements. Remember to calculate the radiator efficiency in British Thermal Units (BTUs) that you’ll need for your radiator. There are calculators online to help. This takes into consideration heat loss through the window/door, type of room and room dimensions to give you an accurate output to match to the size of your new radiator.

Where do you measure a radiator from?

There are four vital measurements to take for your radiator including height, width, left pipe centre to right pipe centre, and wall to pipe centres. Wall distance and wall-to-face are also handy to have.

Repair your home with confidence

As always, our Home Experts are here to help if you need a hand with your radiators, pipes, boiler, or any part of your central heating or plumbing, you can get in touch with us 24/7.


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