Buying an air conditioner to suit the size of room you are trying to cool is very important.
Air conditioners with a large cooling capacity will use more energy, while units that are too small will not cool the room properly, keeping you hot and bothered and drive up your power bill.
The calculation provided are based on floor square meter only. It has not taken into consideration, insulation, large windows, door ways, walk in wardrobes, veranda coverage and ceiling height. Ceiling height may be considered a factor if you have particularly high ceilings, but to keep things simple, just calculate the floor space.