BTU Calculator
Size an air conditioner or heater correctly: the BTUs your room needs based on area, sun exposure and occupancy.
Recommended cooling capacity
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In kilowatts —
Typical unit size —
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How it works
BTU ≈ area × 20, adjusted for sun exposure, insulation and extra occupantsFrequently Asked Questions
How many BTU do I need per square foot?
Roughly 20 BTU per sq ft for cooling: a 300 sq ft bedroom needs about 6,000 BTU, a 500 sq ft living room about 10,000–12,000 once sun and people are factored in.
What happens if my AC is oversized?
It short-cycles: cooling fast but shutting off before dehumidifying, leaving the room cold and clammy while wearing out the compressor. Right-sized beats bigger.
Do kitchens need extra BTU?
Yes — add about 4,000 BTU for a kitchen's appliance heat, and about 600 BTU for each person beyond two regularly in the room. The calculator applies the occupant adjustment.