Enter the room size, ceiling height, insulation, sun exposure and occupants, and get an estimated cooling requirement in BTU per hour with the nearest common air conditioner sizes.
Estimate only. The multipliers are editable assumptions for planning, not a load calculation.
The estimate starts from a base of 20 BTU per square foot of floor area. If the ceiling is higher than 8 ft, the base is scaled up in proportion to the height, because there is more air volume to cool. The result is then adjusted by the insulation multiplier (poor insulation lets more heat in) and the sun exposure multiplier (a sunny room gains more heat), 600 BTU is added for each occupant beyond the first two, and a kitchen adds 4,000 BTU for cooking heat. Common air conditioner sizes run from about 5,000 BTU for a small room unit up to 24,000 BTU and beyond; the result names the smallest common size at or above the estimate. This is an estimate with editable assumptions, not a load calculation: window area, climate and equipment type all move the true figure.
How many BTU are needed per square foot? The common planning figure used here is 20 BTU per square foot of floor area for a room with an 8 ft ceiling, adjusted for taller ceilings, insulation, sun exposure, occupants and kitchen heat. Hot climates and large windows push the real requirement above the base figure.
Why does a kitchen add 4,000 BTU? Cooking appliances release a lot of heat into the room, and the standard adjustment for sizing a kitchen air conditioner is to add about 4,000 BTU on top of the room calculation to cover it.
Is a bigger air conditioner always better? No. An oversized unit cools the air quickly and switches off before removing much humidity, which leaves a room feeling clammy and wastes energy through frequent cycling. Matching the size to the estimated load, and confirming with a proper load calculation for a whole-home system, works better.