How to Measure a Radiator

Last updated: June 8, 2021

So you want to measure your radiator, but you’re not sure where to begin? While radiators are commonplace in most homes across the country, measuring a radiator can be a little tricky without the proper knowledge. And at some point or another, you might need to calculate these measurements if you are moving home or want to upgrade your central heating system.

However, with the right information at hand, it’s a pretty simple job. Measuring a radiator includes measuring the actual unit, the pipework in between, and the distance between the valves. It also includes calculating how much energy you’ll need to heat up a particular room (this is called a BTU calculation and stands for British Thermal Units).

While you might know about measuring height and width, it’s essential that you include all these components when it comes to the radiator measuring process because this will help you to select the perfect radiator for your home.

How To Measure A Radiator

Whether you are shopping for a new model or trying to measure an existing unit, you will want to measure radiators accurately. Mistakes when it comes to measuring can be costly, so you want to get it right. Nothing is worse than ordering a fancy new radiator or heated towel rail only to realise it is entirely the wrong size!

The main measurements you’ll need are radiator height, radiator length, pipe centre dimensions, and the distance between the wall to the pipe centres. With this information, you can find radiators to fit your home and feel confident that your new radiators will slot right in.

So, where do you begin if you want to transform your radiators? Read on!

What You Need

  • A tape measure
  • A friend to help you out (optional)
  • A ladder if you are measuring the width and height of your room to calculate the BTU

Measuring Radiator Height

The first thing you will want to do is measure the height of your radiators, which is a pretty simple task. When measuring, always calculate the highest part of your radiators, as this will ensure that the new model fits in easily. To calculate the height, place your tape measure at the bottom of the radiator (known as the foot) to the highest point.

Height measure will also allow you to see if you have additional vertical space for longer radiators and this might give you some wiggle room to buy a bigger one.

Measuring Radiator Width

Next up, you want to know how wide your radiator is. This measurement will give you essential information on how wide your new radiator can be and help you to determine if you have a little wiggle room for a bigger model. All you need to do is spot the widest part of your radiator and place your tape measure across. Once measured, you might want to measure the free wall area to determine whether you can choose a wider radiator if you so wish.

Measuring Pipe Centres

Now it’s time to measure the pipe centres. “Pipe centres measure?” you might say, and you’re right to wonder what this entails. This is where it gets a little trickier, but don’t worry, with our intel, you’ll be A-okay. The pipe centre is the part of the radiator that’s connected to the plumbing and the central heating system. For ease, you can use these pipes with your new radiator, and as such, you want to measure them correctly. For accurate pipe centre measurement, you’ll need to measure the distance between your radiator pipe centres. For precision, measure from the middle of the right or left pipe inlet to the middle of the other one. If you don’t want to use the pipe centres of your old radiator and need new pipework, this will be a more costly plumbing job. The pipe centre is ultimately the distance between these two pipes.

Measuring Wall To Pipe Centres

Next up, it’s time to measure the wall to pipe centres. This is the distance between the pip centres and your wall, or in other words, how far they are from the wall. Once again, use your tape measure and calculate the distance from the middle bottom of the inlets to your wall. This is important when it comes to selecting an appropriate replacement radiator and will ensure you choose a model that works with the existing pipe centres (if you don’t want to replace them).

Knitted gloves drying on heating radiator

Other Key Calculations For Measuring A Radiator

There are few more critical measurements when it comes to the radiator measure process. For optimal radiators, be sure to remember:

BTU Calculations

British Thermal Units determine how much energy will be needed to heat up one pound of water in degrees Fahrenheit for a particular room. The higher the level of BTU output, the warmer radiators will be – but the more energy it will consume. When choosing radiators or a towel rail, you’ll want to know the BTU calculations for your particular room, as this can impact energy consumption and associated costs. Bigger rooms or homes will require more thermal units to warm them up and can end up costing more. However, if you have a big room, there is no point in buying a smaller radiator that won’t emit enough warmth. To choose an effective heating system that is the correct size and emits the correct energy, you need to know the dimensions of your room.

To work out the number of BTU’s for a specific room or your entire home, you’ll need to know these details:

  • The dimensions of your room (width x length x height) to get the cubic volume
  • The type of room (lounge, kitchen, bedroom, etc.)
  • Additional factors that might impact temperature (such as double glazing, insulated rooms, heated floors)

This information is corroborated and calculated via BTU calculation tools, and the appropriate radiator size for your room can be determined. Luckily, there are many free tools online so you do not need to manually crunch the numbers.

Wall Distance / Wall To Face

Wall distance, also known as a wall to face measurement, calculates the length between your radiator and the wall. It’s also known as the radiator’s projection. This is important so that you don’t order bulky radiators that take up too much room and narrow your space. This measurement is taken from the wall to the furthest point at which the radiator sticks out.

How Do I Know What Size Radiator I Need?

The above factors will determine what size radiator to buy. You will need to calculate the BTU of your room or home to figure out what kind of thermal output you need to properly heat it up. In terms of actual area size, you will need to measure the wall space, pipe centre measurements, your existing radiator, and any excess space.

With knowledge about the physical space available and the required BTU to heat up your home, you should be able to make the right choice when it comes to central heating. When it comes to radiators, this knowledge will ensure that you choose the best device for the job, and your search will be a much simpler feat.

Be sure to always take this information to radiator retailers so that they can help you find the perfect fit.

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