How to Choose a Ductless Mini-Split: Sizing Calculator

How to choose a ductless mini split system - BTU calculator
There is a lot to consider when shopping for a ductless mini-split, but nothing is more important than choosing a unit with the right BTU rating. But what is a BTU rating? How does it work? And why is it so important?

This article will explain why choosing a system with the correct BTU rating is so important. We’ll also share our mini split sizing calculator, which is the easiest way to calculate BTUs.

Mini Split Sizing Calculator

BTU stands for British Thermal Unit and is a unit of measurement used to determine the amount of heating and/or cooling energy a heater or AC is capable of expending. Most cooling product listings will indicate BTU per hour, or BTU/hr, which simply refers to how much energy is expended in one hour of use. 1 BTU is equal to the amount of energy needed to raise or lower the temperature of 1 pound of water by 1° F. So, the higher the BTU listed for a product, the more space that unit is capable of heating or cooling in one hour.

We decided to make things easy for you by providing a handy Mini Split Sizing Calculator on our website. This tool does all the hard work for you and gives you an accurate estimate as to how many BTUs you need to cool your room.

What Size Mini Split Do I Need?

Finding the right BTU rating is essential for properly sizing a mini split system.

Choosing a unit with too low a BTU rating will not cool your room sufficiently, and you will most likely end up overextending your unit trying to do so. Choosing an AC with too high a BTU rating will result in a lot of wasted energy (and money), and so carefully considering the size of the room you wish to cool is crucial in determining your BTU requirements.

In addition to the room’s square footage, there are other factors to consider, as well.

Whether the room gets direct sunlight, for instance, is important to know, because sunny rooms are going to be significantly warmer than shady rooms. The number of doors and windows in a room are also an important factor in determining how much cool air is escaping the room while the unit is in use. Even insulated doors and windows are not air-tight, so the more you have the higher the BTU you will need. A kitchen space or a room close to the kitchen is going to need a unit with a higher BTU rating, and a living room that typically seats six people at a time is going to need a higher BTU than a bedroom that sleeps one or two.

Top Ductless Mini-Split Air Conditioners

Once you’ve determined your BTU needs, it’s time to shop for the actual unit. To get you started, here are Total Home Supply’s top-choice ductless mini-splits, in a range of BTU ratings:

LG LS120HEV1 – 12000 BTU


The LG Mega Series brings all the features of top-end mini-splits down into an easily affordable package, making this unit a great low-cost option for any homeowner. This is a perfect choice for southern regions where heating is not needed at super cold temperatures, and is often used as supplemental cooling in garages, workshops, or additions.

Learn more about the LG LS120HEV1.

Daikin FAQ24PVJU/RZQ24PVJU9 – 24000 BTU


Designed to quietly blend into the ambiance of shops, restaurants, and small offices, this Daikin ductless mini-split is the top choice for commercial applications. Daikin is the world’s top air conditioning manufacturer, so if you are looking for a unit that will last, this is it. SkyAir units are designed with commercial demands in mind, and include a 10-year commercial warranty.

Learn more about this Daikin mini split system.

Daikin 4MXS36NMVJU – 36000 BTU


OutdoorMultiOne of our top multi-zone options, this ductless mini-split from Daikin allows you to cool up to four separate rooms at once.

Learn more about the Daikin 4MXS36NMVJU.

Click here to get the full multi-zone mini split buying guide.

LG LMU36CHV – 36000 BTU

LG-LMU36CHV-2This ductless mini-split from LG is our other favorite multi-zone option, the perfect choice for whole-home comfort. LG offers a wide variety of indoor unit options ranging from 7,000 BTU wall mount units all the way up to 24,000 BTU ducted units. The unmatched flexibility makes this a a great choice for many homeowners.

Learn more about the LG LMU36CHV.

Find Your Mini Split – Next Steps

Be sure to check out our Multi-Zone Mini Split Buying Guide for a thorough explanation of how to find the right mini split for your needs. Then, hop on over to to browse our collection of ductless mini splits.

If you have any other questions or concerns regarding BTU ratings and choosing the best ductless mini-split for you, please do not hesitate to contact us and speak with one of our qualified sales representatives.

Kristen Turner

Featured blogger for Total Home Supply.


Billy Neilan

about 1 year ago

We have a four seasons room facing east which is open to the rest of the house on two sides. The room is 15x19. The rest of the house has a central trane air conditioner. What size mini split should we have installed? Thanks for your help


Mickey Luongo

about 1 year ago

Since the room is open on two sides, it is hard to give an exact estimate of what is needed. I would estimate that you would need about 12,000 BTUs.


holly smith

about 1 year ago

i have an old philly home, 1500 sq feet the duct work does not go up into 2nd and 3 floor well, 2nd floor some in bedroom and 3d floor nothing. I was thinking of getting rid of central air system, really old and buying a multi level unit i dont know what BTU or size or whwere to put in home to cool entire house, 3 floors, kitchen and bathroom are of concern for me- any ideas?


Mickey Luongo

about 1 year ago

The best place to start would be to take a look at our multi zone mini split buying guide. It goes through all the details on how to size and choose a system.



about 10 months ago

We have several estamites on mini-splits (heating/cooling) for our great room which is 800 sq ft. We have one outside door and one window facing north and one outside door and one window facing south. We have estamites going from 15000 btu Panasonic high performance unit to a couple of 24 000 btu unit quotes. From Mitabechi and Carrier. We are confused as to what size to go to. Can you help us? We are told that the Panasonic 15000 btu unit surpasses the other 18,000 units.


Mickey Luongo

about 10 months ago

Based on the size of the space, I would recommend something in the 24,000 BTU range. A BTU is a BTU, so the 15,000 BTU Panasonic would not be equivalent to a larger unit.


Art Bonnell

about 9 months ago

I have a 12 x 14 Sun Room one side open to main house other three sides have 6 foot high Thermopane double glass patio doors and slider windows facing S/W Could you please tell me the BTU I would need in Split Unit for Heat & AC Thanks



about 3 months ago

Hi my living room and my kitchen combine is 14 ft X 23 ft how much btu would I need to cool and heat these two room , thanks


Mickey Luongo

about 3 months ago

Based on the information provided, I would recommend having 10,000-15,000 BTUs


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