Step 1: Room location and size Select Room Location Basement or Ground Floor Room Top Floor or Middle Floor room Room Height Enter the height of your room. Round the height up to the nearest half metre. i.e. if your room is 2.28m high enter 2.5, if it is 3.7 enter 4, etc 2 metre 2.5 metre 3 metre 3.5 metre 4 metre 4.5 metre 5 metre Floor Area Floor Area in Square Metres. Multiply the length of one wall by the length of the wall at right angles to it. (Assuming you have a four-walled square or rectangular room) Step 2: Outside wall or walls with unheated rooms on the other side Select Wall Type Solid Cavity Insulated Length of Outside walls Measure the total length of all solid outside walls or walls with unheated rooms on the other side in metres Step 3: Area and type of window Window type Single glazed Double glazed Total Area of all Windows Add up the area of all single glazed windows in the room in square metres and enter them Calculate Heat Output Required from radiator in watts: Heat Output Required from radiator in BTU/hr: Save result Calculate for another room
