Enter your AC unit dimensions and window measurements — the app checks opening size, mounting clearance, and support bracket requirements.
Whether it fits comes down to the measurements most people skip.
Real openings run about 1 to 2 inches under the labeled size, and a single inch can flip the result. Check your own measurements before you buy or move.
Verdicts compare all six item orientations against the space using verified building standards. See our methodology
“Checked 6 items against our new apartment in 10 minutes. Knew exactly what to order.” — New apartment
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Four numbers decide nearly every fit check. Get these right and the rest follows.
Don't make these
Most “it didn't fit” stories trace back to one of these oversights.
Frequently asked
Size the unit by room area using the ~20 BTU-per-square-foot rule: 100–150 sq ft → 5,000 BTU; 150–250 sq ft → 6,000 BTU; 250–350 sq ft → 8,000 BTU; 350–450 sq ft → 10,000 BTU; 450–550 sq ft → 12,000 BTU; 550–700 sq ft → 14,000 BTU; 700–1,000 sq ft → 18,000 BTU. Add ~10% for sunny rooms, high ceilings, or kitchens. The larger the BTU rating, the wider and heavier the unit — so confirm the matching unit width fits your window opening before buying.
01Window AC dimensions scale with BTU rating. Small units (5,000–8,000 BTU) are about 16–21" wide × 12–15" tall × 15–19" deep and weigh 40–60 lbs. Mid-size units (10,000–12,000 BTU) are about 19–23" wide × 13–16" tall × 19–26" deep and weigh 55–70 lbs. Large units (14,000–18,000 BTU) are about 23–26" wide × 16–18" tall × 26–29" deep and weigh 70–110 lbs. The width is the dimension that has to clear your window opening; the depth determines how far the unit sits inside and outside the sill.
02Most window AC units require a window opening of 23–36 inches wide and at least 13–18 inches of sash opening height. A 5,000–8,000 BTU unit is typically 16–21" wide and fits windows as narrow as 23". Larger 12,000–18,000 BTU units are 22–26" wide and need wider windows. Check the unit's spec sheet for minimum window width.
03Standard window AC units are designed for double-hung or single-hung windows and do not fit casement (crank-out) windows. For casement windows, use a portable AC with a window exhaust hose adapter kit, or look for specialized casement-window AC units (less common and more expensive).
04Many cities (including New York City) require exterior support brackets for all window AC units above the first floor. Even where not legally required, a bracket is strongly recommended for units over 50 lbs. Brackets cost $20–$60 and mount to the exterior wall below the window sill.
05Small units (5,000–8,000 BTU) weigh 40–55 lbs. Medium units (10,000–12,000 BTU) weigh 55–70 lbs. Large units (14,000–18,000 BTU) weigh 65–80 lbs. Portable floor units with exhaust hoses weigh 50–80 lbs but sit on the floor and only need a small window opening for the 5" exhaust hose.
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