Enter your home's square footage and climate to get a rough tonnage estimate — always confirm with a professional Manual J load calculation before buying.
This is a rough sq-ft rule-of-thumb estimate. A professional Manual J load calculation accounts for windows, orientation, and ceiling height, and is the real standard for correct sizing.
An oversized AC unit cools a room quickly but shuts off before properly removing humidity, leaving a home feeling clammy despite hitting the target temperature — correctly sized units run longer cycles that dehumidify effectively. This estimate gives a starting ballpark; feed the resulting BTU/hr into our AC running cost calculator to see the operating cost of the recommended size.
Ceiling height, window area and orientation, insulation, and even the number of occupants all affect actual cooling load — square footage is a reasonable starting estimate but a full Manual J calculation is the professional standard.
It short-cycles — cooling the air quickly but shutting off before adequately removing humidity, leading to a cold but clammy feeling room and more wear from frequent starts and stops.