What size window AC for a bedroom?
A 10×12 bedroom (144 sq ft) needs about 3,600 BTU calculated — retail minimums are 5,000–6,000 BTU. A 9,000–10,000 BTU window unit is the practical sweet spot for comfort and dehumidifying.
What Size Window AC Do I Need?
Window air conditioners are sold in fixed BTU steps — 5,000 through 15,000+ BTU. We calculate your room load so you pick a unit that cools and dehumidifies without short-cycling.
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Sizing settings
Bedroom and office sizing
A 10×12 bedroom calculates to ~3,600 BTU but store minimums are 5,000–6,000 BTU. A 9,000–10,000 BTU window unit is the practical sweet spot for most sleeping rooms.
Compare ductless options in our mini-split vs window AC guide — same BTU math, different install and noise.
Fitting the window opening and egress
Rated BTU must match calculated load — do not buy the largest unit that fits the sash. Oversized window units cool fast but leave humidity high.
Bedrooms used for sleeping must keep an egress path. Measure clear opening height and width after the bracket is installed — some jurisdictions treat a blocked sash as a safety issue.
Humidity, dual-hose portables, and ENERGY STAR charts
Window units usually dehumidify better than single-hose portables because heat leaves through the exterior half of the chassis. Dual-hose portables are closer but still noisier with the compressor indoors — see portable vs window AC.
ENERGY STAR room-AC charts are a solid starting table; this calculator adjusts for ceiling height, sun, occupants, and kitchen load beyond a flat sq-ft chart. For a deeper walkthrough, read window AC BTU sizing.
Related guides
Frequently asked questions
Can a window AC be too big?
Yes. Oversized window units cool fast but leave humidity high. Match rated BTU to calculated load — do not buy the biggest unit that fits the opening.
Window AC vs mini-split BTU — same math?
Room load calculation is the same. Mini-splits are quieter and more efficient but cost more. Use the same BTU result when comparing types.
What size window AC for a 12×12 room?
144 sq ft at 25 BTU/sq ft is 3,600 BTU calculated. The practical window-unit size is 8,000–10,000 BTU so the compressor runs long enough to dehumidify. A 5,000 BTU unit is usually too small for a 12×12 with sun.
Related calculators
HVAC Calculators · https://hvaccalculators.net/window-ac-calculator/