Flagship tool
AC Sizing & Running-Cost Calculator
Most people buy the wrong size. Dial in your room below and watch the recommendation update live — including the AC type that fits and what it'll cost to run each month.
Your room
The floor area of the room you want to cool.
Used for the running-cost estimate.
Recommended cooling capacity
6,500–7,500 BTU
Target around 7,000 BTU for 320 ft² in a hot & humid climate.
Best AC type
Window or portable unit
Est. running cost
$22 /mo
A standard window or portable AC is the cheapest fit for a room this size. Estimated at 8 hrs/day and 0.14 $/kWh — roughly 160 kWh per month.
3 units matched to your room
Compare allFrostline Breeze 8KExtra headroom
8,000 BTU · Window · 12.1 SEER · 52 dB
$279
Zephyr U-Shape 10KExtra headroom
10,000 BTU · Window · 15 SEER · 42 dB
$429
Cumulus Portable 10KExtra headroom
10,000 BTU · Portable · 9.5 SEER · 53 dB
$389
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How we calculate this
We start from the DOE rule of thumb (~20 BTU per ft²) then adjust for ceiling height, sun exposure, insulation quality, occupants and your climate zone. Running cost assumes an EER of 10.5 and your zone's average electricity rate. It's a strong starting estimate — a licensed pro can do a full Manual J load calculation for installs.