Things You'll Need:
- Measuring tape
- Pencil
- Paper
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Step 1
Measure the room dimensions with your measuring tape. This includes the length and width of any walls, as well as the height from ceiling to floor. For rectangular rooms, simply multiple the length of the area by the width. For a triangular area, do the same and divide by two. For unusually shaped rooms, the best technique is to divide the room into easily measureable portions, follow the same steps and add the results later to get the room's entire size.
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Step 2
Measure the area of any windows or doors that do receive direct sunlight. Rooms that receive more direct sunlight than others will normally benefit from a larger air conditioner.
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Step 3
Write down your measurement information. Keep that paper handy for when you shop.
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Step 4
Consider any other factors that may affect the air conditioner, such as whether the room contains any heat producing appliances or the number of people, on average, who spend time in the room.
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Step 5
Using the area of the room and the other data you compiled, there are industry standards that determine the BTUs needed. Use this information at the store or website you plan to buy the air conditioner from, and they will be able to tell you the exact size you need. As an example, a mid-sized room of 350 square feet with normal sunlight would need a 9,000-BTU capacity air conditioner.
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Step 6
Look on the air conditioner itself for the size of the unit in BTUs. The more BTUs an air conditioner offers, the larger the room it can cool.
