Air Conditioner BTU Calculator
Estimate the air-conditioner capacity in BTUs needed to cool a room by its size.
Sizing an air conditioner
Air conditioners are rated in BTUs, a measure of cooling capacity, and matching the capacity to the room is what makes cooling effective. This estimates the BTUs a room needs from its size, so you can choose a unit that will actually cool the space rather than one that is too weak or wastefully oversized.
Enter the room size to see the estimated cooling capacity needed.
Bigger is not better
It is tempting to think a more powerful unit is always safer, but an oversized air conditioner actually performs worse: it cools the room so fast that it switches off before it has removed the humidity, leaving the space cold but clammy, and the frequent on-off cycling wastes energy and wears the unit. Undersized, it runs constantly and never quite cools. Beyond floor area, sun exposure, ceiling height, insulation and how many people use the room all nudge the figure.
Frequently asked questions
Is a more powerful air conditioner better?
No — an oversized unit cools too fast to remove humidity, leaving the room cold but clammy, and cycles wastefully. Right-sizing matters.
What besides room size affects the BTUs needed?
Sun exposure, ceiling height, insulation and how many people use the room all adjust the figure up or down.
Is anything uploaded?
No. The estimate happens in your browser.