BTU & Air Conditioner Size Calculator
Cooling capacity a room needs, adjusted for the things that matter.
A sizing estimate. A proper Manual J load calculation accounts for window area, orientation, air changes and local climate.
How it works
The starting point is around 20 BTU per hour per square foot of floor, then adjusted: less for shade, more for sun, +600 for each occupant beyond two, and +4,000 for a kitchen.
Oversizing is the common and expensive mistake. An air conditioner that is too large cools the air quickly, satisfies the thermostat and shuts off before it has removed any humidity. The room ends up cold and clammy, the compressor short-cycles, and it wears out early. Slightly under is better than substantially over.