Summer is known for its warmer climate, and it's during this season that people like going out to enjoy the sun and maybe going to the beach and taking a dip in the sea. However, according to The Weather Channel's forecast, this year's summer in the United States will be hotter than before.

Similarly, in other parts of the world, such as Southeast Asia, people are expected to experience scorching hot heat waves in the years to come, as a result of a study first published in 2021 in the Geophysical Research Letters. You might then want to keep those swimsuits away for now and just stay at home and chill in a properly air-conditioned room.

Use this air conditioner BTU calculator, or AC BTU calculator, to help you decide what size of the air conditioner to buy, so you can efficiently cool your room. Of course, the choice of brand and air conditioner type still depends on you. But we'll help you find the recommended output power of the AC that will best suit your room.

Know your recommended AC capacity, whether in BTU/hr (British Thermal Units per hour), horsepower (hp) or Watts (W) using our calculator. To accomplish that, let's first take a look at the room you are planning to install your air conditioner in.

What size of air conditioner should I get for my room?

An image of a room with an installed air conditioner.

So, you finally decided to buy or upgrade your air conditioner to keep your room from getting too hot. While deciding to regulate the temperature and humidity of your house is the easy part, it is a good thing to know that air conditioners come in many different sizes.

The importance of choosing the correct air conditioner size

Choosing the right air conditioner for a given room size is essential 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.

This air conditioner room size calculator will help determine the recommended output power your air conditioning unit needs to function perfectly. Of course, this depends on the room's area, the average number of people regularly in the room, and its exposure 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 your room's length and width. 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
(ft²)
Recommended air
conditioner capacity
(BTU/hr)
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. Input it into our air conditioner room size calculator to apply any necessary adjustments. 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 people regularly in the room. Our bodies tend to release heat into the environment, affecting the cooling effect of an air conditioner. The table above is suitable for 1 to 2 people in a room. We need to adjust the recommended BTU per hour capacity of the air conditioner by about 600 BTU/hr for each additional person.

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

Finally, 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 one pound of water's temperature 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.

Once you've chosen what size of an 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 fan's 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. If you rather need to heat your room, you may want to check out our furnace size calculator.

Kenneth Alambra
Choosing the right size of air conditioner not only allows you to properly cool your room but can also help you efficiently use energy. ⚡ Use this calculator to know the recommended air conditioner size for your room, or to check if your current air conditioner is enough or too much for your room. 🙂
I want to...
purchase an air conditioner.
Room configuration
Room type
Bedroom
Sunlight exposure
Neither shaded nor sunny
Illustration of the sunlight's location while using the air conditioner on the selected room type.
Number of people in the room
Room size
Room length
ft
Room width
ft
Room floor area
ft²
Ceiling height
ft
Results
Purchase an air conditioner with a cooling capacity of at least:
Recommended air conditioner size
hp(E)
This will ensure a properly cooled space and an efficient energy consumption. 🙂
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