How Many BTU Air Conditioner Do I Need (Room Air Conditioner)

Using the wrong size room air conditioner will not cool your room efficiently. That’s why it is imperative to buy a unit that matches the square footage of your space.

With that in mind, you must be wondering, “what size air conditioner do I need?” No need to worry. This article will answer your question directly.

In this case, we will look at two units: a window air conditioner and a portable air conditioner.

Room Air Conditioner BTU Sizes

A window air conditioner’s capacity usually ranges between 5000 to 24000 BTU. On the other hand, a portable air conditioner often ranges between 5000 to 15000 BTU.

Room air conditioners are relatively smaller compared to central air conditioners. The size of a central ac ranges between 18000 to 16000 BTU.

The Estimation Method: How Many BTU Do I Need

According to the rule of thumb, you need 20 BTU per square foot. So, you can use the BTU calculation formula for air conditioner to find how many BTU per square foot you need.

How do you calculate the square feet of a room? You can get the area of your room by multiplying its length by its width.

What Size Window AC Do I Need?

We will use the estimation method above to show you how to calculate the size window ac you need for your room.

Example: How many BTU do I need for a 12x12 room?

First, a 12x12 room equals 144 square feet. Then, we will multiply the area (144 sq ft) by 20 BTU (rule of thumb).

144 sq ft x 20 BTU = 2,880 BTU

In short, for a 12x12 room needs at least 2,880 BTU. The most common minimum size for Windows AC sold on the market is 5000 BTU. So, you need a 5,000 BTU window AC to cool a 12x12 room.

Window AC Size Chart (BTU to Air Conditioner Room Size)

Consult the following window ac size chart to get a direct answer corresponding to your specific room size.

Window AC BTURoom Size (sq ft)
1,000 btu 50
5,000 btu 250
6,000 btu 300
6,500 btu325
7,500 btu 375
7,700 btu 385
8,000 btu400
9,000 btu 450
9,500 btu 475
10,000 btu 500
11,000 btu 550
12,000 btu 600
14,000 btu 700
14,500 btu 725
15,000 btu 750
18,000 btu 900
22,000 btu 1100
24,000 btu 1200

This is a table of Window AC BTU to Room Size. The BTU sizes listed here are common BTU sizes for Window AC products in the market. If you can find the area of your room listed in the table above, you can get your answer directly. Here is an example.

Example: How many BTU for 600 sq. ft.?

On the table, the corresponding window air conditioner size is 12,000BTU.

But if you can’t find the exact size of your room on the table, go for the closest option. Look at the following example.

How many BTU for 1,000 sq. ft.?

You can’t find the exact room size on the chart. However, the closest option is 1,100 sq. ft. So, you will need a 22,000 BTU window air conditioner to cool a 1,000 sq. ft. room.

How Many Tons of Portable AC Do I Need?

Here, we will also use the rule of thumb: 20 BTU per square foot.

Example: How many BTU do I need for a 20x20 room?

Step One: Get the square feet by multiplying its length by its width, which is the area of the room.

20 x 20 = 400 square feet.

Step Two: We will multiply 400 by 20 to get the cooling capacity.

400 sq ft x 20 BTU = 8,000 BTU.

In other words, you will need a 8, 000 btu portable air conditioner to cool a 20x20 room.

Portable AC Size Chart (BTU to Air Conditioner Room Size)

You can use the portable ac size chart below to check how many BTUs you need for your specific room size.

Portable AC BTU (DOE)Room Size (sq ft)
1,000 btu 50
5,000 btu 250
6,000 btu 300
6,500 btu 325
7,000 btu 350
7,500 btu375
8,000 btu400
8,500 btu 425
10,000 btu 500
11,000 btu 550
12,000 btu 600
13,000 btu 650
13,500 btu 675
14,000 btu 725
15,000 btu 750

Find the right size portable ac by choosing the BTU value that corresponds to the area of your room on the table.

Example: How many BTU for 500 sq. ft.?

The corresponding ac capacity on the chart is 10,000 BTU. Therefore, you will need a 10,000 BTU portable air conditioner to cool a 500 sq. ft. room.

Again, you should choose the closest room size if you can’t find the exact one on the chart.

Example: How many BTUs do I need to cool a 450 sq. ft. living room?

The closest room size on the table is 425 sq. ft. Therefore, you will need 8,500 BTU to cool a 450 sq. ft. living room.

How Big Is My Room Air Conditioner?

Room air conditioners come in a variety of sizes. And it is often difficult to figure out what size suits your room best.

Luckily, you can also use the rule of thumb to calculate how many square feet a room air conditioner can cool. We will demonstrate using an example.

Example: How many square feet does a 5,000 BTU air conditioner cool?

20 BTU can cool one square foot. So, you need to divide 5,000 BTU by 20 to get 250 per sq. ft.

You will get the same answer if you use tables above.


Size matters when buying a room air conditioner. Buy a size too small or big, and the unit will struggle to keep the room at a comfortable temperature. The correct size ac will run efficiently while making you feel comfortable.

It can be hard to choose the right size window or portable air conditioner with so many options in the market. Hopefully, this article has made it easier to pick the best unit for your cooling needs. If you are ever in doubt, you can always revisit the charts above.


Here are some of the most frequently asked questions.

1. What is the difference between BTU DOE and BTU Ashrae? And BTU SACC VS DOE?

BTU Ashrae is the older rating used in portable ACs, while BTU SACC is the new rating that the department of energy introduced in 2017.

A portable ac blows hot air outside, creating a vacuum that sucks in warm air through the window or cracks. That lowers the efficiency of the unit.

BTU SACC is lower since it accounts for that decrease in cooling capacity. For example, the Whynter 11000 BTU Dual Hose Portable Air Conditioner from Whynter has an Ashrae rating of 11,000 BTU and an SACC rating of 6390 BTU.

Remember, always use the BTU DOE when buying room air conditioners.

2.What is the highest BTU air conditioner for 110/220 volts?

The highest BTU air conditioner for 110V volts is 15,000 BTU. Meanwhile, the highest BTU air conditioner for 220V is 23,000 BTU.

3. How to tell if an outlet is 110 or 220?

220V circuits have two hot wires colored black and red. Therefore, they have two hot terminals. On the other hand, 110V circuits have one hot wire that is colored black. So, they have one hot terminal.

4. How to get 220V from 110V? How to use a 220v appliance in a 110V outlet?

In many cases, you may need an electrician to upgrade the wiring in the home. However, you can create 220V from 110V using a step-up converter. Just connect the convertor to two separate sources of 110V to produce one 220V.

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