BTU Calculator: What Size Air Conditioner Do I Need? |
Shop All Air Conditioners

BTU Calculator: What Size Air Conditioner Do I Need?

Air Conditioner AssortmentWhen you're shopping for a new air conditioner, finding the best BTU level for the soon-to-be-cooled room is a very important step. We've got some answers to common air conditioner questions, plus an A/C BTU calculator to allow you to figure out the best possible air conditioner size!

Calculate the number of BTUs you need

Select the room size in square feet

Select the number of people typically in the room

Is the room a kitchen or on the second floor?

Select ceiling height

Select the room size, typical number of occupants, kitchen/second floor, and ceiling height.


What is BTU in an A/C?

A BTU, or British Thermal Unit, is the amount of energy needed to raise 1 pound of water by 1 degree Fahrenheit while at sea level. When it comes to air conditioners, the BTU rating tells you how many BTUs per hour the machine can remove from the air. The higher the rating, the more high-intensity the cooling.

What if I Use Too Low of a BTU for the Room Size?

If the air conditioner is too small for the room, it can't bring the room to a comfortable coolness level. The unit will be running constantly without hitting the proper temperature and dehumidification levels, making it extremely inefficient and costly.

What if the BTU Rating is Too High?

In order to create a comfortable temperature, an air conditioner must be able to dehumidify the air as well as cool it. Using an air conditioner that's too big for the room will result in it shutting off early without allowing the space to properly dehumidify, and the excess moisture will create an uncomfortably damp environment.

What's the Best BTU Calculation Formula for an Air Conditioner?

Simply measure the room's square footage and ceiling height, plug it into our BTU calculator, answer a few other questions, and your answer will appear!

How Do I Measure Square Footage of a Room?

To calculate a room's area in square feet, simply multiply its length by its width. For instance, if the room is a rectangular 10 feet by 20 feet, the area would be 200 square feet. If the room is a perfectly-square 20 feet by 20 feet, the total area would be 400 square feet. Don't worry about factoring height into this equation – it'll be a separate measurement on our air conditioner BTU calculator.

Do I Need to Do Anything Differently for a Portable A/C?

You do not, and you should be aware that 2018 has ushered in a new and more accurate BTU rating system for portable units!

I've Measured My Room's Area and Ceiling Height, and I'm Ready for the BTU Calculator!

Excellent – scroll to the top and get started!

Related Content
Air Conditioner Installation: True Wall Fit

Air Conditioner Installation: True Wall Fit

Do you have a thick wall that’s greater than the standard construction size? Learn how a true wall fit air conditioner is a great solution in this video.
Air Conditioners: Through the Wall Installation

Air Conditioners: Through the Wall Installation

There are many things to consider when installing a through-the-wall air conditioner.
How to Calculate the BTU for Your Room Air Conditioner

How to Calculate the BTU for Your Room Air Conditioner

Need an air conditioner, but not sure what size is the right size? This video covers helpful tips on how to determine the proper BTU size.
Close Navigation
just a moment...