BTU Calculator
Size an air conditioner for a room in BTUs.
Cooling capacity needed
6,000 BTU/hr
In tons
0.5
Typical window unit
5,000–12,000 BTU
20 BTU per square foot, adjusted
The Energy Star baseline is ~20 BTU per square foot, tuned for sun (±10%), extra occupants (+600 each beyond two), and kitchens (+4,000). A 300 sq ft bedroom lands near 6,000 BTU — a modest window unit.
Bigger is not better
An oversized AC cools the air before dehumidifying it, short-cycling into a cold, clammy room and higher bills. Sizing slightly under and letting it run steadily gives drier air and longer equipment life — insulation and ceiling height shift the number too.
Frequently asked questions
- How does the BTU Calculator work?
- Size an air conditioner for a room in BTUs.
- Is the BTU Calculator free to use?
- Yes. The BTU Calculator is completely free, runs entirely in your browser, and requires no account or sign-up. Your inputs never leave your device.
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