How to calculate the needed BTU for AC?

You might check out Consumer REPORTs at the library. In their review of ac's they usually discuss sizing.

Just one room? Look on the box that AC's are in at the store. It is not perfect, but damned good guide for 85% of homes. Just add or subtract it you are in special circumstances, like living over a dry cleaner or bakery. In 85%=, small bedroom, 5,000 Btu. Medium, 6,000, large, 8,000.

Considering the whole house? Proper calculation requires knowing insulation, outside temperatures, window areas, exposure, occupancy, etc. It must be done right for good results.

Don't buy too large a unit thinking it will cool faster or better. It won't properly handle the humidity. Ed snipped-for-privacy@snet.net

I'm no expert, but I've heard as a ballpark figure, use one ton of cooling per 500-600 square feet. One ton = 12,000 BTUs, so 20-24 BTUs per square foot. My bedroom has about 210 square feet, so 4200 to