How to Choose the Right Size Radiator for Any Room

Whether you’re making home improvements or upgrading your radiator, knowing its size is crucial.

Read on to learn about how to measure your radiator, what size you need, and considerations before replacing it.

How to measure your radiator

To do this, you’ll need a tape measure and your phone (to make notes).

There are four key measurements you need and two optional ones. All of these should be noted down in millimeters.

Diagram showing how to measure a radiator, with five labelled measurements: 1. Height — a vertical arrow on the left side from the top of the radiator body to the bottom pipe connection; 2. Width — a horizontal arrow along the bottom from the left pipe to the right pipe; 5. Depth — a short arrow at the top-right corner showing the front-to-back thickness of the radiator panel; Wall pipe — an upward arrow indicating the right-hand pipe connection; and a zoomed inset in the bottom-right corner showing measurement 4, wall pipe to centre, which is the horizontal distance from the wall surface to the centre of the pipe.

1. The radiator’s height

Measure from the lowest point of your radiator to the highest.

2. The radiator’s width

Measure from the furthest point on the left to the furthest point to the right of your radiator.

3. The left pipe centre to the right pipe centre

That’s the distance between the two pipe inlets that feed into, and out of, your radiator.

4. The wall surface to the pipes’ centres

This is a useful measurement if you aren’t altering any plumbing as part of the radiator replacement process. Begin at the wall and measure the short gap between the wall to the centre of the pipes.

5. Depth (optional)

Two extra measurements that can also be useful are the depth of your current radiator.

If it sticks out, you might consider replacing it with a slimline version.

6. Space is behind your radiator (optional)

To do this, simply measure the distance between the wall and the radiator.

What size radiator do you need

Radiators traditionally were previously made to standard sizes. But in recent years, they are not.

In the UK, radiator efficiency is calculated in British Thermal Units (BTU).

This calculation is the ideal radiator-to-room size ratio needed for your radiator to sufficiently heat the room.

It takes into account the size and the type of room.

You can even work out the BTU for your whole house! (This is helpful when it comes to buying a new boiler.)

The table below can help you estimate the correct BTU to correctly heat the rooms in your home.

Infographic from YourRepair explaining how to calculate radiator size in BTUs by room type: lounge/dining room (multiply cubic feet by 5), bedrooms (multiply cubic feet by 4), common areas like hallways or kitchens (multiply cubic feet by 3), with a 10% deduction for double glazing.

Does your radiator need replacing?

You may be replacing your radiator as you renovate or redecorate your home. Or perhaps you’re changing your central heating system.

But if you’re considering replacing it because it doesn’t work well, first consider whether it can be repaired. You might simply need to bleed your radiator or get a powerflush. Or you perhaps your boiler isn’t working properly, which is cutting the heat your radiator can output.

So, you should first call out a plumber or engineer.

And if you have boiler cover, you’ll be able to get the problem diagnosed and fixed.

We offer unlimited repairs to YouRepair plan customers and our affordable plans start from as little as £8 a month.