BTU Calculator

How do you know what size of radiator you need in your room?

Radiators have become more efficient in the last 10 years, giving off more heat for the same physical height and width. So when replacing a radiator in a bedroom, bathroom or kitchen, you might not need the same physical size of radiator you had there before. You don't want to under-estimate your heat requirements, either. It would be horrible to get out of the shower and shiver!

Radiators are constructed in different ways which affect the heat they can give off.  This is down to things like the amount of surface area, the flow of the hot water through the radiator, how the radiator convectors are joined to the radiator, or even if they have them at all!  So, radiators aren't about size, they're about the amount of heat they give off. 

And the clever people have kindly worked out a mathematical formula for figuring out what output of radiator you'll need in each room of your house.  All you have to do is answer the questions, then hit the calculate button.

The formula takes into account the size of the room, what it's used for and how much extra heat loss happens because of large windows, being on the cold side of the house and whether or not you have double glazing.

Once you've calculated the number of BTUs you need for the room, we've made it easy for you to find the radiator you need - just click on the type you want - a towel rail, a standard panel radiator, or something a little bit special - a designer radiator. Our special system will take you to all the radiators that will be suitable for the heat output you need for your room.