What Size Air Conditioner for 300 Square Feet?

A 300 sq ft room (about 17 × 17 ft) needs about 7,000 BTU of cooling, so look for an 8,000 BTU air conditioner. A very sunny room needs 7,700 BTU, and a kitchen 11,000 BTU.

Change any number below to match your project. The ac btu calculator works for any size.

Room size

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How it's worked out

  1. The ENERGY STAR chart lists 250 to 300 sq ft at 7,000 BTU per hour.
  2. Adjust for the room: +10% for strong sun, −10% for heavy shade, +600 BTU for each regular occupant past two, +4,000 BTU for a kitchen, and scale up for ceilings over 8 ft.
  3. Pick the nearest common unit size at or just above the result.

300 sq ft: size by room conditions

RoomBTU neededUnit to look for
Normal room7,000 BTU8,000 BTU
Very sunny (+10%)7,700 BTU8,000 BTU
Heavily shaded (−10%)6,300 BTU6,000 BTU
4 people use it (+1,200)8,200 BTU8,000 BTU
Kitchen (+4,000)11,000 BTU12,000 BTU
9 ft ceiling (+12.5%)7,900 BTU8,000 BTU

Don't oversize much. A unit that's too big cools the air quickly and shuts off before it pulls out the humidity, so the room ends up cold and clammy.

Other common sizes

More detail: What Size AC Do I Need? BTU and Tons by Square Footage