A quick and easy way to calculate the size of the radiator required for any room in your home is by measuring the room in metres (length x width) to find the m2 and then entering the information into our BTU radiator size calculator. You can also use the tables provided to estimate the radiator size required to correctly heat your room. Don’t forget to measure your ceiling height as this impacts the size required. When purchasing Rointe electric radiators, it is important to remember that the success of our heaters is down to the correct sizing.