Each size unit on the website specifies the room size it caters for. You can calculate the square meterage of your room by multiplying the length x width. If your installer who delivers the unit determines the size of unit is too small for the application for which you intend to use it he will recommend that you exchange it for a bigger sized unit. He will then take the unit back and return it with a bigger size, or you can return the unit to Fourways Online via the installer for a full refund by Fourways Online provided your unit is in line with requirements listed as per return stipulations)