Need help? Call us: 0333 009 4040

The Best Prices to Buy

Shopping Cart |

BTU Calculator

Find the perfect radiator to heat your room with the BTU calculator. Find the optimum number of BTUs required for your room and create that warm, cosy temperature without

What does BTU stand for? What does BTU mean?

BTU stands for British Thermal Units and is a unit of measurement for energy. Example: 150 BTU is equal to the amount of energy used to raise the temperature of 150 pounds of water 1-degree Fahrenheit. You will see BTU used when referring to the amount of heat a radiator emits to raise the temperature in a room. The higher the BTU number associated with a radiator, the more heat that radiator can produce to warm the room.

You can calculate the BTU needed to heat a room with a BTU Calculator. You can get a rough idea based on just the dimensions of the room but for more accurate results all you need to know is;

  • Room Dimensions Including ceiling height
  • Number of windows in the room
  • Window Size
  • Type of window glazing (single or double usually)
  • Number of walls on the outside of the building
  • Outside wall material
  • What is above and below the room

Finding the perfect radiator with our BTU Calculator

Use the BTU calculator to find out the BTU requirements of each room you are adding or replacing radiators in. Remember the number that the calculator returns is the total number of BTUs required, so you can use as many radiators as you would like to reach this number.

If you are concerned at all, we always recommend going above the BTU number. Some houses or buildings are just naturally colder than others and you are the best judge of that. Going over your total BTU number does no harm except you could make it too hot if not using a thermostat or your bills could be unnecessarily high, again, unless you use a thermostat. Not having enough however could result in your heating being on full power and still not achieving the cosy feeling you are striving for.

We always recommend working with a plumber to get an expert’s opinion on site but our detailed BTU calculator works brilliantly and allows you to achieve an accurate guide as to how many BTUs and Watts you need to heat your room effectively and efficiently.

Once you have filled out all of the fields and clicked “calculate” our smart calculator will do the hardword for you and display the radiators that are suitable for your needs.

From there you can use the filter on the left to narrow your search down to the perfect size, colour and style.

Room Dimensions

Width* Height* Length*
Window Area X² (Calculate this by multiplying window height by window length)

Room Information

Type of room:


Where are you heating?

What is below the room?

Think about the flooring of your room, and whether there is another room below

What is above the room?

Where applicable, choose the amount of insulation

Select type of outside wall:

This helps us calculate how much heat the room might lose

Select type of window:

This also helps us determine the expected heat loss in the space

Select number of outside walls (Optional) :

Your Requirements
BTU's Required
Watts Required