How do you know how many Air Conditioner BTU's you need for your room size?

Question

There is a formula I just dont know it.

Answer 1

The size of the room is not the only important factor. You should take under consideration the heat loss. Is you room insulated properly? Do you have a source of heat inside and so on. It is a complicated procedure. From my experience do not say I need 14,000 BTUs lets put 18kBTUs to be sure. You will make the room to cold and unconfortable.

In my house I have used seperate units for each room. For bedrooms I have used 9,000 BTU units (they are about 12-15 sq meters each). I also have a open plan living room with the kitchen (about 70 sq meters). I used a 24kBTU unit and it was a mistake. A 18 kBTU would be fine. On the second living room which is bigger but does not have a full-sized kitchen I use a 18kBTU unit and is perfect. (Sorry for the metric units if you do not use them)

Take a look at the links. The first has a good calculation method.