❄️ BTU Calculator
Estimate how many BTUs of cooling capacity your room needs and find the closest matching air conditioner size.
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Your Result
This is a rough sizing estimate. Actual cooling needs vary with local climate, ceiling height, room shape, and appliance heat load. Consult an HVAC professional for a precise load calculation.
How the BTU Calculator Works
A BTU (British Thermal Unit) measures how much heat an air conditioner can remove from a room per hour. Sizing an AC unit correctly matters — an undersized unit will run constantly without cooling effectively, while an oversized unit cools too fast without properly removing humidity.
Formula
+ 600 BTU per occupant beyond 2
+ 1,000 BTU per window beyond 2
Suggested AC Sizes
Air conditioners are manufactured in standard capacities. This calculator rounds your required BTU up to the nearest common unit size: 5,000, 6,000, 8,000, 10,000, 12,000, 14,000, 18,000, or 24,000 BTU.
Frequently Asked Questions
How many BTUs do I need per square foot?
A common rule of thumb is about 20–25 BTUs per square foot of living space, adjusted for insulation, sun exposure, ceiling height, occupants, and heat-generating appliances.
What happens if my AC is oversized?
An oversized air conditioner cools the room quickly but shuts off before properly dehumidifying the air, which can leave the room feeling cool but clammy.
Does ceiling height matter for BTU sizing?
Yes. Taller ceilings mean more air volume to cool. This calculator factors in ceiling height as part of the overall room sizing guidance, though the core estimate is driven primarily by floor area.