Window Air Conditioner Size Guide

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A Guide for choosing the right size AC unit

Over the years, the most common question we hear is “what BTU size air conditioner is right for me?”. It’s a common question because there are so many variables that go into choosing the right size. We created this guide to help you make the right choice.

Why Choosing The Right Size AC is Important

What’s the big deal, right? It’s a big heavy piece of metal that goes in the window and makes cold air! While it’s true that they are heavy, choosing the wrong size can cause your room to be way too hot, or way too cold.

  • Too Small: If you buy or rent an air conditioner that is too small for your room, the unit may not be effective at all in cooling your room. Cold air might be coming out, but the appliance will be over working (running up your electric bill) and take hours to make the room slightly cooler.
  • Too Large: If you buy or rent an AC that is too large, mainly you are just over paying for what you need. Additionally, your room might become an ice box. 
How Do I Determine What BTU AC I Need?

There are two steps to finding the right sized window AC:

Step 1:


Start by determining your room size. How large is the room(s) you are trying to cool? If you know what size room you have, you can reference the following chart:



Square Feet

Room Type

Recommended AC Size (BTUs)

AC Size (BTUs) for extra cold

150 sqft

Small Bedroom

5000 BTU

6000 BTU

250 sqft

Medium Bedroom

6000 BTU

8000 BTU

350 sqft

Large Bedroom

8000 BTU

10,000 BTU

450 sqft

Medium Room

10,000 BTU

12,000 BTU

550 sqft

Large Room/Studio

12,000 BTU

15,000 BTU



If you don’t know what size your room is, you can use this guide to estimate:


Bedroom or home

SQ. FT. 100-300

Primary bedroom or playroom

SQ. FT. 250-400

Living room, family room, or open plan

SQ. FT. 350-650

Step 2:


Step up 1-2 sizes in the chart above if:


  • The room or apartment is on the 2nd floor or higher. Heat rises, so you will want to go up one size in the chart above to account for that.

  • The room or apartment is on the top floor. The dark roof absorbs sunlight so you will need a higher BTU AC to manage the extra heat.

  • You receive direct sunlight (greenhouse effect). Usually if your windows are west-facing for the afternoon sun, you’ll want to jump up a size in the chart above.

  • You like it especially cold.



Hopefully this guide will help you choose the right AC for your needs. You can always reach out to us if you have questions at


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