Wondering what size radiator you need for your room?

Look no further than our BTU Calculator. BTUs, or British Thermal Units, are used to measure radiator efficiency. Calculating the required BTU / Watt output of your radiators is crucial to ensure your space is heated efficiently and comfortably.

Your Questions About Calculating BTUs

So, how do you calculate your room's BTU requirement?

Our calculator takes into account factors such as room dimensions, window size, and
wall material to determine the combined heat output of all radiators and/or towel rails in your room. Larger rooms may require more than one radiator to adequately heat the space.

But what exactly is a BTU?

Essentially, it's the amount of energy required to heat one pound of water from 39°F to 40°F. It's roughly equal to 1.055 KJoules, or the amount of heat produced by burning a single wooden match from end-to-end. 10 years ago in Ireland most plumbers spoke of BTU output for radiators, but now we use BTU and Watt interchangeably.

How do I convert between Watt and BTUs

To convert Watt to BTUs, multiply by 3.412. To convert BTUs to Watt, divide by 3.412.

Does my radiator need the exact output to match my room?

Choosing the right radiator size is crucial to ensure your room is heated efficiently. We recommend selecting a radiator size that is within a 10% range of your calculated BTU/Watt requirement. If you have to choose between a radiator that is too small or one that is too big, it's always better to choose the latter. You can always turn a larger radiator down if necessary, but a smaller radiator won't give off enough heat to adequately warm your space.