Is this room a kitchen?
Room orientation
neither shaded nor sunny
Room characteristics
Length of room
Width of room
Ceiling height
Room floor area
Number of people in the room
Recommended air conditioner size
Air conditioner capacity

This air conditioner room size calculator, also known as an AC BTU calculator, will help you decide what size of air conditioner to buy so you can be efficiently cool (or heat) your room. Of course, the choice of brand and air conditioner type still depends on you; this air conditioner calculator can only provide you the recommended output power of the AC, in British Thermal Units per hour (BTU/hr) by default, for your room.

You can also convert the output power into horsepower (hp) or Watts (W) which we also have calculators as well. But first, let's take a look at the room you are planning to install your air conditioner in.

How to choose what size of air conditioner to get for any room size

An image of a room with an installed air conditioner

So, you finally decided to buy an air conditioner to keep your room from getting too hot (or maybe too cold). While deciding to regulate the temperature and humidity of your house is the easy part, air conditioners come in a lot of different sizes, and choosing the wrong one could end up wasting you money or time, having to go back to the store for a replacement.

This air conditioner room size calculator will help you determine the recommended output power your air conditioning unit needs to do everything perfectly. This depends on the room's area, the average number of people regularly in the room, and the orientation of the room with respect to the sun.

If you do not know your room's covered area yet, you can find it by using any measuring tools you have lying around, and measuring the length and the width of your room. Input these values in our air conditioner room size calculator to instantly get your room's area. If you have an irregularly shaped room, you can use our square footage calculator and choose the multiple rooms option to help you determine the area of your room.

Once you know the area of your room, check the chart below for its corresponding recommended base air conditioner capacity:

Room Area
Recommended air
conditioner capacity
100-150 5,000
150-250 6,000
250-300 7,000
300-350 8,000
350-400 9,000
400-450 10,000
450-550 12,000
550-700 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

After knowing your base air conditioner capacity, you also have to measure how high your ceiling is, and apply any necessary adjustments. Input it into our air conditioner room size calculator to have it considered. We need to add 1000 BTU/hr for each foot if the ceiling is over 8 feet tall.

Next, we also have to consider the number of persons that are regularly in the room. Our bodies tend to release heat into the environment, which can affect the cooling effect of an air conditioner. If a room is regularly occupied by more than two persons, we need to adjust the recommended BTU per hour capacity of the air conditioner by about 600 BTU/hr for each additional person.

Finally, we also need to consider the location of the room and its type (whether it's a bedroom or a kitchen, etc.). If you are installing the air conditioner in a kitchen, we need to add an 4000 BTU/hr adjustment to the recommended air conditioner capacity. This adjustment is to compensate for the heat that emanates from the refrigerator and other kitchen appliances.

Other than that, we also need to consider the heat coming from the sun. If your room is facing the sun during the day, we need to increase your air conditioner's capacity by 10%. However, if your room is shaded or faces away from the sun during the day, you can opt for a smaller air conditioning unit by decreasing the recommended capacity by 10%.

Understanding Air Conditioning British Thermal Units (AC BTUs)

The British Thermal Unit, or BTU, is a unit of heat that we use to classify the capacity of a cooling or heating appliance. One British Thermal Unit is the amount of heat energy required to raise the temperature of one pound of water by 1°F.

Nowadays, we use this unit to classify the capacity of air conditioning units and other similar devices or products that deal with energy consumption or conversion. If you are keen to learn more about air conditioning British Thermal Units (AC BTUs), and how to be more efficiently cool rooms, you might want to visit our heat loss calculator.

The importance of choosing the correct air conditioner size

Choosing the right air conditioner for a given room size is very important if you want to minimize your electricity bill. A small air conditioner will have a hard time cooling a large room, or it might not be able to cool it at all. On the other hand, choosing a huge air conditioner could cool the room very fast, but won't dehumidify the room at all. This particular instance leaves the room cold and, at the same time, clammy, which is not comfortable at all. Therefore, it is crucial to decide what size of air conditioner you need before buying one.

Once you've chosen what size of air conditioner to buy, you might want to check its estimated power consumption using our electricity cost calculator. If you are also currently using an electric fan, you might also want to check the Advanced mode of our fan calculator. By combining these two tools, you can check your electric fans current energy consumption.

Want to learn more about cooling your room?

If you fancy learning more about cooling your room, and are interested in the physics behind it, why not check our Newton's Law of Cooling calculator? You'll learn more about it there.

Kenneth Alambra
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