BTU Calculator

Choose one of the following:

Home BTU calculator

Enter Square Feet of your entire Home:

0 square feet

How many occupants in your home?:

1 people

Roughly, how old is your house?

Would you describe your climate as:

Do you have a basement?



This calculator should only be used to estimate your building’s BTU needs. You should get a professional BTU estimate done by your local HVAC company to get a better picture of what size unit you need.

Room BTU calculator

Enter Square Feet of Room to be Cooled:

100 to 150 square feet

How is the Room Insulation?


Is the Room Very Sunny?

Is This Air Conditioner for the Kitchen?



This calculator should only be used to estimate your building’s BTU needs. You should get a professional BTU estimate done by your local HVAC company to get a better picture of what size unit you need.

AC Unit background

What Size Air Conditioner Do I Need?

Using an air conditioner on a hot day can make the temperatures more bearable, but only if the air conditioner is big enough to cool the area you want it to. On the other hand, purchasing an air conditioner that is too large for the space may mean you’re spending more money, both on the unit and on the energy it requires to run. Get the right-size air conditioner for your needs and make sure you’re comfortable – both physically and financially.

Determining Your BTUs

Air conditioners are sized by the number of BTUs they put out. BTUs stand for British Thermal Units and refer to the amount of energy your air conditioner is using per hour.

To figure out what size air conditioner you require, you first need to determine the amount of BTUs you require. This is done by calculating your square footage.

Break up each room into as many squares and rectangles as you need to be able to measure the entire space accurately. This means separating out closets, bump outs, and hallways each as their own separate area.

Need To Buy A New AC Unit OR Heater?

Selecting Your Unit

Air conditioners are clearly labeled with the amount of BTUs they need. Consult the following chart to see where your square footage lands in relation to the amount of BTUs. Purchase the unit that best corresponds to the amount of square footage you have.


100 – 150

150 – 250

250 – 300

300 – 350

350 – 400

400 – 450

450 – 500

500 – 700

700 – 1,000

1,000 – 1,200

1,200 – 1,400

1,400 – 1,500

1,500 – 2,000

2,000 – 2,500
















Variations and Variables

While this chart is used as a general rule of thumb for selecting air conditioner size, variations can occur depending on several variables you need to consider.

Shade and Sun

If the room or house you are cooling is heavily shaded, you may need 10 percent fewer BTUs to cool it. If the house or room is very sunny, however, add 10 percent more BTUs.

Room Occupancy

The more people that use the area you are cooling, the higher the BTUs need to be to compete with body heat. As a general rule of thumb, for every person over an initial 2 people, add 600 BTUs.

Hot Appliances

If the room you are planning on installing an air conditioner in is the kitchen, you need to factor in additional BTUs for the stove, oven, and microwave. Add about 4,000 BTUs to the unit size to cover this.

Get a Professional Opinion

If you are unsure about the size of unit you need, or you have trouble calculating the size of area you plan to cool, get a professional opinion. Getting the right-sized air conditioning unit is too important to leave to chance.

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Testimonials & Reviews

See What Our Customers Have to Say

    • Testimonials - Brett Walker
      Brett Walker

      I wanted to make sure my air conditioner was ready for summer. Fernando came out and made sure my unit was tip top. He was friendly, professional and not a sales man. Thanks Fernando!

    • Testimonials - Jackie Barkenhagen
      Jackie Barkenhagen

      Colin and Andrea were incredibly professional and knowledgeable. They did a great job representing the company. We will definitely contact them again for any HVAC needs that arise.

    • Testimonials - Nick Corso
      Nick Corso

      We woke up in the middle of the nite on memorial day to a hot house. I called precision at 6am and they were here before noon. Simple problem fixed, cool house. I love these guys!

    • Testimonials - Jeneen Piche
      Jeneen Piche

      Thank you Ray at Precision Air...the compressor on our AC went out last night and the house was HOT. This morning Ray was there to replace the compressor and had us feeling the cool air again in no time. Great customer service...quick response time and friendly from the first call until the repair was completed. Ray even offered to clean the filters! Thank you!!

    • Testimonials - Cara Perlman
      Cara Perlman

      I’m so glad I called Precision for my annual AC checkup!! Austin was professional, super friendly and answered all my questions. I’ve had more bad experiences with AC companies here in the valley than good ones. Precision Air will have all my hvac business going forward!! Thanks for being a reputable and honest company!!!

    • Testimonials - Jeff Stanczak
      Jeff Stanczak

      He did a great job; professional and knowledgeable! Kalin is the technician’s name and Precision Air and Plumbing should take a bow for hiring such an invaluable employee!!!

    • Testimonials - Kingsley Evans
      Kingsley Evans

      Precision Air is a company of integrity. I signed up with them August 1st, 2019 for their AC maintenance plan for 2 years... Someone from their office called me a week ago to set up their yearly maintenance visit. SO GRATEFUL.

    • John Andres - Precision Air & Plumbing
      Andrew Burkhart

      Precision Air and Plumbing is a wonderful company to work with! They are very experienced and professional. They have helped us in our home for many years via a/c service and air duct cleaning.

    • Testimonials - David Topping
      David Topping

      It was time to replace our AC, and so our choice was Precision Air, as we've been with them for over 20 years. Teman & Julian did an excellent job on the installation today, arriving on time.

Contact Us

Feel free to contact us any time at 602-349-6922 for immediate assistance.

We offer 24 hour emergency service, and would be happy to schedule an appointment for you, or simply answer any questions you may have.

Precision Air & Plumbing

3045 N. Colorado St.
Chandler, AZ 85225

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