BTU Calculator
Find the Correct AC Unit for Your Home
Your new air conditioner needs to be big enough to cool the area you want, but not too large – which means more money up-front and unnecessarily higher energy bills. Air conditioners are sized by British Thermal Units (BTUs) and refer to the amount of energy your air conditioner is using per hour.
Choose one of the following:
To figure out what size AC unit you require, you first need to calculate the square footage of your home. Break up each room into as many squares and rectangles as you need to be able to measure the entire space accurately. The chart below shows the correlation between square footage and BTUs:
| Square Footage | BTUs Required |
|---|---|
| 100 - 150 | 5,000 |
| 150 - 250 | 6,000 |
| 300 - 350 | 8,000 |
| 350 - 400 | 9,000 |
| 400 - 450 | 10,000 |
| 450 - 500 | 12,000 |
| 500 - 700 | 14,000 |
| 700 - 1,000 | 18,000 |
| 1,000 - 1,200 | 21,000 |
| 1,200 - 1,400 | 23,000 |
| 1,400 - 1,500 | 24,000 |
| 1,500 - 2,000 | 30,000 |
| 2,000 - 2,500 | 34,000 |
Variations and Variables
While this chart is used as a general rule of thumb for selecting air conditioner size, variations can occur depending on several variables you need to consider.
Shade and Sun
If the room or house you are cooling is heavily shaded, you may need 10 percent fewer BTUs to cool it. If the house or room is very sunny, however, add 10 percent more BTUs.
Room Occupancy
The more people that use the area you are cooling, the higher the BTUs need to be to compete with body heat. As a general rule of thumb, for every person over an initial 2 people, add 600 BTUs.
Hot Appliances
If the room you are planning on installing an air conditioner in is the kitchen, you need to factor in additional BTUs for the stove, oven, and microwave. Add about 4,000 BTUs to the unit size to cover this.
Get a Professional Opinion
If you are unsure about the size of unit you need, or you have trouble calculating the size of area you plan to cool, get a professional opinion. Getting the right-sized air conditioning unit is too important to leave to chance.
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