Air Conditioner BTU Calculator

Created by Kenneth Alambra
Reviewed by Bogna Szyk and Jack Bowater
Last updated: Sep 10, 2023

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. Do you also need to find the volume of the room? Check the cubic yard calculator for that purpose!

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)





























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%.

You should now know everything crucial about air conditioning. So, let's also go outside! Our incredible fence calculator explains everything in detail on how to tackle the problem of fencing your yard.

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. The air conditioning British Thermal Units (AC BTUs) are important power units, mostly used for heat transfer. If you plan to build a house, think about a suitable insulation material, and if you decide to use bricks, then our brick calculator should be a helpful tool. On the other hand, the tank volume calculator offers a quick estimation of the water volume you need to heat, e.g., in a swimming pool you plan to construct.


How big of a room will a 8000 BTU cool?

Between 300–350 ft² or about 30 m². If the room is higher than 8 feet, however, you need to add 1000 BTU per foot over that height.

How do I calculate what air conditioner size I need?

To estimate the air conditioner size you'd need to cool a specific room:

  1. Measure the square footage or area in square meters of the room.
    • For that, multiply its length by its width. If using meters, multiply the result by 0.092903.
  2. Multiply this by 25 BTU to get your air conditioner size.

What does BTU mean in air conditioners?

BTUs are used to rate an air conditioner's cooling capacity. The higher, the better. BTU stands for British thermal unit, which is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. A rate of 8000 BTU/h in cooling systems means the air conditioner will remove 8000 BTU of heat each hour.

How much electricity does an air conditioner use?

On average, air conditioners use about 3000 W while running. So, turning a 3000 W air conditioner on for a whole day will consume 72 kWh per day.

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
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
Room width
Room floor area
Ceiling height
Purchase an air conditioner with a cooling capacity of at least:
Recommended air conditioner size
This will ensure a properly cooled space and an efficient energy consumption. 🙂
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