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BTU / AC Size Calculator

Cooling capacity you need for a room.

Details

Results

Recommended cooling
In tons
Room area

Estimates — add extra for waste and confirm with your supplier.

How it works

A common rule is about 20 BTU per square foot, adjusted for sun exposure and extra occupants. We convert to tons (12,000 BTU = 1 ton) so you can size a unit.

Oversizing isn't better — too big a unit short-cycles and won't dehumidify well.

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Good to know

FAQs

How many BTU per sq ft?

About 20, adjusted for sun and occupancy.

What's a ton?

12,000 BTU/hr of cooling capacity.

Does sun matter?

Yes — sunny rooms need more, shaded rooms less.

Is this exact?

No — a sizing estimate; a Manual J load calc is precise.