What size AC for a 12×12 bedroom?
A 12×12 room is 144 sq ft. At 25 BTU/sq ft that is 3,600 BTU calculated load — but retail units start at 6,000–9,000 BTU. A 9,000 BTU mini-split or window unit is the practical minimum for most bedrooms.
AC Size Calculator
“What size air conditioner do I need?” usually means BTU for a bedroom or living space. Enter dimensions and we show calculated load plus the practical retail size — window unit, portable, or mini-split.
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Why calculated BTU differs from store shelf labels
A 10×10 bedroom calculates to ~2,500 BTU but stores sell 6,000–9,000 BTU as the minimum practical unit. That is normal — the unit runs at part load most of the time on inverter or cycling compressors.
For a 12×12 bedroom (144 sq ft), a 9,000 BTU mini-split or equivalent window unit is the standard recommendation.
Oversized AC problems
Too much capacity cools the room in minutes without running long enough to remove humidity. You get a cold, clammy space and higher bills. Match rated BTU to calculated load — do not double “just to be safe.”
Our mini-split vs window AC guide compares efficiency and noise at the same BTU rating.
Frequently asked questions
What happens if AC is too big?
Oversized units cool quickly but do not run long enough to dehumidify. You get a cold, clammy room and higher energy bills. Size to calculated load, not “bigger is better.”
Window AC vs mini-split sizing — same BTU?
The BTU load calculation is similar. Mini-splits are more efficient and quieter but cost more upfront. Match rated BTU to calculated load for either type.
Related calculators
HVAC Calculators · https://hvaccalculators.net/ac-size-calculator/