window ac unit, buying guide

Choosing The Right Size Window Air Conditioner.

Selecting the correct BTU's Is simple

1. Determine the room's square footage

Determining the floor square footage of the area to be cooled takes simple math.  Just use the following formulas.
9 in = .75 ft. 6 in = .5 ft. 3 in = .25 ft.
Always measure in feet, converting the inches to fractions of a foot For example: 12 ft., 6 inches, is 12.5 ft.

Square and rectangular rooms:

Multiply the full length of the room by its width.

Triangular rooms:

Multiply the length of the area by the width and divide by two.

Complex room shapes:

Sub-divide into squares, rectangles and triangles.  Then use the formulas above to determine the total square footage.

3. Adjust as necessary

Make any adjustments for the following circumstances:

Heavy shade icon
If the room is heavily shaded, reduce capacity by 10 percent.
very sunny icon
If the room is very sunny, increase capacity by 10 percent.
If more than two people regularly occupy the room, add 600 BTUs for each additional person.
If the unit is used in a kitchen, increase capacity by 4,000 BTUs.

Consider where you install the unit. If you are mounting an air conditioner near the corner of a room, look for a unit that can send the airflow in the right direction.


Now you should have the SQ FT Of The Room.

2. Find the correct cooling capacity for your room size

Area To Be Cooled (square feet)Capacity Needed (BTUs per hour)
100 up to 1505,000
150 up to 2506,000
250 up to 3007,000
300 up to 3508,000
350 up to 4009,000
400 up to 45010,000
450 up to 55012,000
550 up to 70014,000
700 up to 1,00018,000
1,000 up to 1,20021,000
1,200 up to 1,40023,000
1,400 up to 1,50024,000
1,500 up to 2,00030,000
2,000 up to 2,50034,00


Installing The Window AC

Do I need to have my AC installed by an insured professional:

  • You live in a highrise building
  • Your building or landlord requires it
  • The AC unit is to heavy for you to lift
  • The AC unit is to complex for you to install
  • You don't have the tools for the job

You can learn to Install the AC unit by searching for videos on Youtube AC installation Videos


Type Of AC For My Window

Double-Hung Windows

Window AC installation

Learn More

Casement Windows

Casement Air Conditioners
Casement Air Conditioners

Learn More

Through-The-Wall AC

Friedrich WallMaster, (built-in sleeve required)

Learn More

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