BTU Calculator - Find your perfect radiator with our heating calculator

BTU & Watt Calculator

Find your perfect radiator

Select one or more from the drop downs to get started.


With the help of our BTU calculator, you can determine how much heat energy is needed in each space, per hour - so you can maintain a pleasant temperature without wasting any energy or money.

All you need to know are the room's measurements and the number and kind of windows. The calculator will then inform you of the size radiator you require to get the ideal level of warmth in your space.

Please Note: This is just a guide for reference only Larger Rooms, such as living rooms that may require more than one radiator positioned throughout the room. If this applies to you, divide the required output between the number of radiators required. This BTU Calculator produces results for Delta T 50.

Wat is BTU (British Thermal Unit)?

The United States and the United Kingdom accept this as a unit of measurement for energy and it is now used instead of Watts (W). A BTU is defined by a quantity of heat required to raise the temperature of 454 grams of water from 60 to 61 degress Farenheit. BTUs/h are normally used in the definition of the cooling power of air conditioning systems as well as the heating of power fuel.

For W to BTU/h conversions, 1 W is equal to 3.41 BTU/h. Moreover, to convert BTU/h into Watts you need to divide by 3.41; to convert Watts into BTU/h you need to multiply by 3.41.

How To Use Our BTU Calculator Tool?

Using our BTU Calculator is pretty simple. The calculator works by factoring in the following aspects of your space:

  • Firstly, after you've entered you're infomation, it determines the room's cubic capacity by multiplying the length, width and height(in feet or metres) from the data that you provide.
  • Secondly, further mathematical equations are then added to the mix by our clever BTU calculator based on the infomation you input for other factors, such as the type of room (lounge/dining room, kitchen, bathroom, or bedroom), as well as whether or notit has a north-facing wall, double-glazed windows and patio doors.
  • Lastly, the calculator will provide the answer, which is split into two parts: the first part is a range between two BTU values, and the second is a range between to Watt values. This then gives you a precise radiator sizing guidance for the space, so you can be sure that your radiator has a heat output within those limits, it will have the capacity to warm (and keep warm) the space both pleasantly and affordably

Need Assistance?

To meet the BTU requirement, keep in mind that you can eithe rcombine many radiators or settle with just one. If you have any questions regarding our BTU calculator, please don hesitate to Contact Us today. Our friendly staff are always happy to help.