Air Conditioner BTU Calculator
Find the right air conditioner size for a room. Enter the dimensions and fine tune for sun exposure, the number of people and a kitchen to see the recommended BTU and tonnage.
How to size a room air conditioner
- Enter the room length and width in feet.
- Pick the sun exposure: normal, sunny or shaded.
- Set how many people use the room and flag a kitchen if needed.
- Read the recommended BTU per hour and tons to choose a unit.
Examples
15 by 20 ft living room
300 sq ft, normal sun, 2 occupants, not a kitchen
6,000 BTU per hour, about 0.5 tons
Frequently asked questions
How many BTU do I need per square foot?
The common rule is 20 BTU per hour per square foot. A 300 square foot room needs about 6,000 BTU, then you adjust for sun, people and heat sources.
Why does sun exposure change the size?
A room with lots of sun gains extra heat, so it needs roughly 10 percent more capacity. A heavily shaded room needs about 10 percent less.
Is a bigger air conditioner always better?
No. An oversized unit cools fast then shuts off without removing humidity, leaving the room cold and clammy. Right sizing keeps the air dry and comfortable.
How many BTU are in a ton of cooling?
One ton equals 12,000 BTU per hour. So a 24,000 BTU unit is a 2 ton air conditioner, which this tool reports for you.
Do high ceilings need more cooling?
Yes. The rule assumes 8 foot ceilings. Taller ceilings hold more air, so capacity scales up with the extra height.
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