The heat output or ‘BTU’ (British Thermal Unit) calculator is a great way to work out how much radiator power you need. There are several factors which can affect this, such as room dimensions, heating levels and types of window, which are all covered in our radiator BTU calculator. Please note: You may need several radiators for bigger rooms.

Our BTU (British Thermal Units) calculator will help you to work out the heat requirement for your room, and recommend the number of radiators you will need to comfortably heat it.

What is a BTU?

A British Thermal Unit (BTU) is a measure of heat output from a radiator. Depending on the size of your room, the number and type of windows and what the room is used for, you’ll need more or less heat. If you have a higher BTU requirement, it might be better to use more than one radiator to deliver the heat you’ll need to a room. The total BTU output of several smaller radiators may meet your needs.

How do I choose the right radiator?

The BTU value of all our radiators is clearly in our webstore helping you find those which suit your requirements.


How to work out the correct BTU output for your room

  1. Take into account the type of room you are looking to heat—is it a bathroom, bedroom, kitchen, dining room, living room or hallway?

Different room types, generally, require slightly different temperatures. Here are some typical examples below (but you may prefer your room to be warmer or cooler):

  • Living Room/Dining Room: 21-22°C/70-72°F
  • Bathroom: 21°C/70°F
  • Kitchen: 20°C/68°F
  • Bedroom/Hallway/Cloakroom: 18°C/65°F
  1. Measure the length, width and height in metres and note this down. (If you have an odd-shaped layout, divide the room into separate rectangles and measure each one separately)
  2. You are now ready to perform your BTU calculation, using the tables below: