Measure the square footage of a room with a tape measure. Square footage is obtained by multiplying the length times the width. As an example, a 12footby12foot room is 144 square feet.
How to Measure for the Correct Size Air Conditioner
All air conditioners are measured by the amount of their cooling capacity, or BTUs (British Thermal Units). Central air conditioners are rated by the ton, with each ton equal to 12,000 BTUs. Conversely, room or portable air conditioners are measured just by the BTU rating of the unit. You can measure for the correctsized air conditioner for use in either either a specific room or a whole house by doing simple mathematical calculations.
Things You'll Need
 Tape measure
Instructions


1

2
Determine the correct air conditioner needed to cool off the area measured. An air conditioner rated between 7,000 and 10,000 BTUs will cool a 100 to 200squarefoot room. An air conditioner rated between 9,000 and 12,000 BTUs will cool a 250 to 350squarefoot room. An air conditioner rated between 12,000 and 16,000 BTUs will cool a 350 to 450squarefoot room.


3
Reduce or increase your BTU calculation if special circumstances apply. If the room is shaded by trees or buildings, reduce the amount of calculated BTUs by 10 percent. If the room is on the sunny side of the building or on the second floor, increase your BTU calculations by 10 percent.

4
Add 600 BTUs for any room calculation if there will commonly be more than two people in the room at the same time.

5
Increase the BTU measurement by 4,000 BTUs if the air conditioner will be located in a kitchen.

6
Add the measurements of all the rooms sizes together. Allow for kitchens and secondstory rooms, then calculate how many tons you will need on a central air conditioning unit for wholehouse cooling.

1

Tips & Warnings
 The higher the Energy Efficiency Rating of an air conditioner, the more efficient it will be, and the less it will cost to run over extended periods of time.
References
 Photo Credit Jupiterimages/Photos.com/Getty Images