How Many BTU Do I Need? (Air Conditioner Room Size Calculator)

There are several metrics you should consider before buying an air conditioner. You have different EER and SEER ratings, power, amperage, voltage, and so on.

The most important metric is the cooling capacity (measured in BTU/hr). It denotes the size of your air conditioner.

BTU meaning: British Thermal Unit or BTU/h is a unit that determines the cooling/heating power of an HVAC device (air conditioner, furnace, etc.).

What is BTU is an AC unit? Simply put, it’s the capacity or power of the AC.

The bigger the BTU, the more cooling effect an AC unit can provide.

Here is an example of how you can calculate how many BTUs you need to cool down a 500 sq. ft. area with 8 feet ceilings, average sun exposure, average climate, and not including kitchen (you can find this BTU calculator below and use it for your situation; with 4,000-24,000 BTU room size table):

example of size of air conditioner calculator in btu h


In short, you would need a 10,000 BTU air conditioner.

How many BTUs do you need to cool down certain square footage of space properly?

There are only 2 rules:

The BTU needed to cool down a room of known footage that can be calculated. According to The U.S. Department Of Energy recommendation for the size of room air conditioners:

“…an air conditioner generally needs 20 BTU for each square foot of living space.”

Based on room size, ceiling height, and other conditions, you can calculate how many BTU air conditioner you need:

Air Conditioner BTU Calculator

Calculated BTU:

0.00 BTU


As you can see, the sq ft to BTU converter neatly gives you an idea of what size of air conditioners you should be looking at in an ‘sq ft to BTU’ kind of way.

measuring rooms for air conditioner btu size
Roughly measure the places in which you want to enjoy the cool air thanks to your new AC unit.

If you want to properly cool down a 300 square foot area (or room), you need a 6,000 BTU air conditioner. Obviously, the problem arises when you have a tiny 12×12 room, for example. According to the US Department of Energy directive, an air conditioner’s most appropriate size would be 2,880 BTU unit. The best you can do here is to buy a small 5,000 BTU window or a small 8,000 BTU portable AC unit (more about the smallest AC units here).

The trendy portable air conditioners, for example, have a cooling capacity of 6,000 BTU to 14,000 BTU. According to Go Downsize, the average size of studio apartments in the US is about 500 sq ft. That means that for a small apartment, you don’t need expensive central air conditioning. You can install an average-sized 10,000 BTU portable air conditioner, which will save you tons of money.

Pro tip: Always buy a little bigger AC unit than this recommendation. Example: When you use the BTU calculator below and get, let’s say, 10,000 BTU for a 500 sq ft area, start looking for a 12,000 BTU air conditioner. Your electricity bill will be a little higher, but you won’t need to sweat if you bought an AC unit that’s too small.

To better illustrate what size of an air conditioner you need, let’s have a look at a BTU chart:

Air Conditioner BTU Chart; With 12,000 BTU (1 Ton) Room Size Example

Question: What is the 12,000 BTU air conditioner room size? 12,000 BTU is equal to 1 ton; we’re talking about 1 ton AC room size. 

Answer: Using the EPA’s 20 BTU per sq ft rule of thumb, the room size of 12,000 BTU air conditioners is 600 sq ft. Equally, 1 ton AC room size is about 600 sq ft. 

Here is a table with rough room size estimates for air conditioners with different cooling capacities to help you out:

Cooling Capacity (BTU):Room/Area Size:Examples:
4,000 BTU air conditioner room size:100-200 sq ft10x10 room, 12x12 room, 14x14 room
6,000 BTU air conditioner room size:200-300 sq ft16x16 room, tiny apartment
8,000 BTU air conditioner room size:300-400 sq ft18x18 room, 20x20 room
10,000 BTU air conditioner room size:400-500 sq ft22x22 room, small studio apartment
12,000 BTU air conditioner room size:500-600 sq ft24x24 room, average studio apartment
14,000 BTU air conditioner room size:600-700 sq ft2 rooms, small apartment
16,000 BTU air conditioner room size:700-800 sq ft2 rooms, average apartment
18,000 BTU air conditioner room size:800-900 sq ft3 rooms, above average apartment
20,000 BTU air conditioner room size:900-1,000 sq ft3 rooms, larger apartment
24,000 BTU air conditioner room size:1,000-1,200 sq ft4 rooms, large apartment

Again, when narrowing down your choice of an air conditioner, knowing how big an area you need to cool is your best friend. Based on that, you can calculate sq ft to BTU and immediately know what range of BTU values your perfect AC unit should be.

If, for example, you buy a 14,000 BTU portable air conditioner to cool down a 12×12 room, you will have a chill cold room and more than $100/year unnecessary cost on your electricity bill.

Perfect BTU Air Conditioner For Room Sizes

As recommended by The U.S. Department of Energy, the ballpark figure is 20 BTU per sq ft. That is a very good estimate already.

The simplest BTU calculation formula for an air conditioner looks like this:

BTU = Number of sq. ft. * 20

However, to get a perfectly-sized air conditioner with just right enough cooling power and no energy overspending, you should consider some additional factors. These are:

  1. Room height.
  2. Local climate.
  3. Sun exposure.
  4. The number and size of the windows.

The BTU calculator and chart work best for standard room height. Obviously, if you have a tall ceiling (older buildings have +10 ft ceilings), you have to add a bit of cooling power in BTU.

There is also a difference if you live in Texas or New York. The local climate in Texas is, on average, hotter, and therefore you should need an air conditioner with a few 1,000 BTU more.

The same goes for sun exposure. If the room or area you’re looking to cool down is generally facing the sun, you will need a bigger air conditioner.

Additionally, the walls do block the sun very effectively. Windows don’t. If you have big windows and many of them, the sun will heat your house more.

In summary, when do you need an air conditioner with higher BTU than standardly recommended:

  1. If you have high walls.
  2. If you live in a hot climate. Examples: California, Texas, Florida, New Mexico, and so on.
  3. If the particular room you want to cool down is facing the sun more often than not.
  4. If you have an above-average size and number of windows.

Example: If you have a 500 sq ft sun cabin near Texas with many glass windows, you should be looking at 10,000 BTU air conditioners (as recommended). It would be best if you were looking at 14,000 BTU portable air conditioners, for example.

What Does BTU Mean In Air Conditioners (Summary)

BTU in air conditioners is simple a metric of how much cooling effect that particular AC unit can produce.

We want an air conditioner that has just the right amount of cooling effect. That’s why by knowing the square footage of the area we want to cool down, we can calculate how many BTUs should our air conditioner have.

The equation for ‘sq ft to BTU‘ is quite simple – multiply the sq ft with 20. That means that a 500 sq ft room needs a 10,000 BTU air conditioner. Of course, do make sure to buy an AC unit that is a bit stronger if you have high ceilings, live in a hot climate, and have an above-average sun in those rooms.

You should use the BTU calculator when choosing different types of air conditioners, including:

We hope this helps. If you have any questions about your particular room or area you’re buying an air conditioner for (and don’t know how many BTU ones you should take), you can ask in the comments, and we’ll try to give you an answer as soon as possible.

94 thoughts on “How Many BTU Do I Need? (Air Conditioner Room Size Calculator)”

  1. I have a 15 ft by 15th room with a 9ft ceiling. This room has a door way that goes into another 12 by 13 room.the door way is average size. What btu would you recommend.thank you for your time.

    • Hello David, 15×15 and 12×13 rooms have a combined area of 381 sq ft. Given the additional doorway and above-average ceiling height, you’re looking at a 9,000 BTU unit. 10,000 BTU with an above-average airflow (above 250 CFM) would be a safe bet. Hope this helps.

  2. I am researching the most efficient portable room air conditioner for a 2nd floor, sunny bedroom. The 13’2” by 14’5” bedroom room has cathedral ceilings, a SW facing window that measures 48” by 56” and one occupant. Due to HOA restrictions and a sliding glass window, I plan to get a portable air conditioner. I’ve read about dual hose conditioners and not sure if that’s the best way to go. I’m not sure how to calculate the necessary BTU’s needed. Can you help with any thoughts on this? Thank you, Sue Harig

    • Hello Sue, the 13’2” by 14’5” room has about 190 sq ft. Let’s assume that the cathedral ceiling has a height of 13 ft. Such a bedroom has the same volume as a 310 sq ft room with an 8 ft ceiling height. That would, roughly speaking, require a 6.200 BTU portable AC unit. With that big sliding glass window and a lot of sun, the safe estimate for the most optimum AC unit would be 7.000-8.000 BTU.

      The dual hose portable air conditioners have two key advantages: superb energy-efficiency and they don’t lower the pressure inside the room while running. However, they tend to be bigger – 14.000 BTU or so. If you can find a 8.000 BTU dual-hose one, that would be a very optimum choice. Hope this helps.

  3. Hi David , I have a 25×17’ room with 8’ ceilings in all
    Adjacent hallway with 30 “ doorway hallway is 9×5
    Then doorway into lr and dr 30×21
    There is a wall between lr and dr with a 6 ‘ doorway
    How many btu would I need

    • Hello Peggy, for a 25×17 room (425 sq ft), you would need a 8.500 BTU portable AC. If you add 9×5 hallway (45 sq ft) and LR + DR 30×21 (630 sq ft), the total calculated area is 1.100 sq ft. Roughly speaking, you would need 22.000 BTU cooling power. Portable AC units will hardly handle it, window units or mini split units could do that job well.

  4. Thank you for the useful advice. My small apartment has openings in the wall for AC in the living room and the bedroom, thus I am debating whether to get one 14,000 BTU AC or two smaller ones. Any advice on the subject is appreciated.

    • Hello there, if you need 14,000 BTU AC, one window unit or one mini-split unit would be the best choice. AC units above 15,000 BTU usually need an electric upgrade; which you won’t need here. On the other hand, you can invest in two portable AC units, each of 7,000-8,000 BTU, but those can take some space and need to be vented out of the window. The most elegant solution would be a 14,000 BTU mini-split unit.

    • I have an area that is 850 sq feet and another room that is 300 sq ft. I want to purchase a unit for each area. How many BTUs do I need for each area and how big a condenser will I need to accommodate both with a multi unit condenser?

      • Hello Ruth, for 850 sq ft you would need a 17,000 BTU device and 6,000 BTU device for the 300 sq ft room. The best option would be to use a 2 zone mini split AC unit (1 outdoor unit with 2 indoor units, one in each room). 2 zones should have a capacity of 17,000 BTU and 6,000 BTU respectively. Such a combination, quite frankly, is hard to find; the most common 2 zone unit is 12,000-12,000 BTU.

  5. Hi there. Question… I’m living in a one bedroom apt in NYC. The AC unit will be for our living room. The living room itself is about 20’7″ x 12.1″. However, it has large windows and on the other side of the living room, there is a kitchen (that doesn’t have any AC). Your advice would be much appreciated!

    • Hello Grace, for the (roughly speaking) 350 sq ft living room you would need a 7,000-8,000 BTU AC unit. However, the kitchen is additional space and for kitchen you usually have to add 4,000 BTU. All in all, 12,000-14,000 BTU would make sense in this situation. You can opt for portable or window AC unit; mini-split unit would be a bit too much.

    • Hello Jackie, 16 x 14 room is 224 sq ft. If we assume a 9 ft high ceiling, average climate and average sun exposure, you’re looking at 5,000-6,000 BTU units. For this size, a smaller portable air conditioner would be most appropriate. You can find some of the best portable AC units here.

  6. I have a 16×16 bedroom on the second floor with 8′ ceilings. My current wall unit is 15 years old and has ALWAYS made the room feel damp. I was told the unit is too big for our size room. I went to local store to size one more appropriately and was told the Frigidaire FFRE153ZA1 15,000 BTU’s is the right one. Of everything I read online, it seems to me that this is too big? Am I correct? What size wall unit would best suit my needs and what Frigidaire wall mounted model am I looking for?

    • Hello Michael, 16×16 bedroom has a total area of 256 sq ft. That means a 5,000-6,000 BTU would be enough. You are right; the 15,000 BTU unit is definitely an overkill for a single room. Conservative choice would be the old Frigidaire FFRA051WAE 5,000 BTU. However, given that you have problems with high humidity, a stronger Frigidaire FFRE0833U1 8,000 BTU makes sense (it comes with 1.7 pints per hour dehumidification; it can draw more than 40 pints of water per day). Hope this helps.

      • I have a 26 by 30 room 10 ft walls plus 3 ft to ceiling sun hits direct it’s 780sqft how many btus is recommended going to install two ceiling fans thanks

        • Hello Carlos, with 10 ft ceiling the two fans is a good idea. The room has quite a volume; you would need about 25,000 BTU devices. 2 12,000 units might do the trick as well.

          • So I can just put a 30000 btu minisplit would that work is a 36000 btu unit too much thank you

          • Hello Carlos, the 30,000 BTU mini-split will do the job very well. It’s always better to have a little bit bigger capacity than a little bit too weak a unit. 36,000 BTU would be an overkill.

  7. I live in New York. My small apartment is 600 square feet but is broken up into 2 bedrooms, 1 living room, 1 kitchen, 1 hallway, bathroom. I have lots off walls and ceiling is just under 9 feet high. I want to buy a mini split ac system. Would an 18000 BTU unit split into 9000/9000 work? 1 in the front bedroom, 1 in the back bedroom…and leave doors open during the day?

    • Hello Andrew, several rooms, hallways, and kitchen do add to the overall BTU cooling power. You’re right; you would need at least 15,000 BTU device – a 18,000 BTU would be perfect. Two-zone 9000/9000 mini split would be the perfect solution here. You do have to have the door open in order to ensure smooth air circulation. It seems that you already have exactly the right idea what to do.

  8. Live in Central California Modesto it gets super hot in the Summer I’m in a 23 by 25 master using a 5,000 btu. I’m thinking of getting an 8,000 btu the 5,000 btu just isn’t cutting it. I have three windows one being a huge 12 by 6 and it’s located to the west the whole window gets very hot midday. Should I get the 8,000 btu?

    • Hello Edward, you’re correct, the 5,000 BTU unit is not enough. 23×25 master bedroom is 575 sq ft. Given that you’re in sunny California with 3 windows, even the 8,000 BTU might not be enough. For your situation, a 12,000 BTU or even 14,000 BTU would be recommended.

  9. I have an enclosed patio room, it is 20 by 15′ with large windows on three sides. What size portable uni
    t do I need?

    • Hello Harold, for a 300 sq ft patio you would need 6,000 – 8,000 BTU unit. Portable air conditioner would probably be the most convenient.

  10. Good Morning. I have a office room size of 22ft x 30 ft with ceiling height of 9 ft. No direct sunlight but evening sun rays through two glass window. How much BTU do I need to cool the room? Is there any standard that the temperature of the room should within a particular time and what other specifications do I need for a AC while buying like CMH, Cooling Capacity.

    • Hello Sivaram, a 660 sq ft room with low sun exposure would need, roughly speaking, 14,000 BTU AC unit. The only standard for BTU size is the EPA recommendation of about 20 BTU for every 1 sq ft of a room; other factors may apply as well. In your situation, a 14,000-15,000 BTU should do the job well.

    • Hello Kerwyn, we have to do a bit of sq m to sq ft conversion here. 100 m2 living room is equal to 1076 sq ft. With +4,000 BTU for the kitchen, you’re looking at 28,000 BTU device. 30,000 BTU to be safe.

    • Hello James, the usually 15,000+ BTU mini split units need run on 220V. If you’re looking at a 12,000 BTU 220V model, there is a chance the same mini split is available with 115V and double the amperage. The key here might be the heater. If it’s a 18,000 BTU heater, for example, the whole unit will usually need 220V.

  11. I have a Sunroom that’s 17 Ft. by 17 Ft. with a ceiling height 8 1/2 Ft.
    3 of walls are all glass top to bottom. ( room built 1963 ) It also has a very heavy Sun exposure. Located above this added on room is an open attic… can you help

    • Hello Hugh, that’s one hell of a room. Standard 300 sq ft room, for example, would need at least 6.000 BTU device. With the added 1/2 ft of the ceiling and the 3 windows, you should probably check out 10,000 BTU units.

  12. Hi,
    I’m looking to use a portable air conditioner in my garage. Its 683 sq ft with an 11 ft ceiling. I live in central North Carolina. Direct sunlight on insulated garage doors during the afternoon. Garage walls are foam insulated. Four windows, three of which get direct sunlight. Windows are doubled pane. Cement floor. According to your BTU calculator I would need 18,837.5 BTUs. Not sure if they make that size AC in a portable? So, would two 10,000 BTUs work or 14,000 BTUs work just as well?

    • Hello Daryl, the biggest residential portable AC units have a maximum cooling capacity of 15,000 BTU. It’s an electrical thing; if you want 15,000 BTU+, you would need 220V instead of 115V, or alternatively, you would have to double the Amps, which is not ideal. In your situation, you would probably need two units, yes. 2 x 10,000 BTU would make sense. Maybe a combination of 14,000 BTU and 8,000 BTU would be smarter; you only run 14,000 BTU most of the time but during a really sunny day, you also turn on the 8,000 BTU unit.

  13. Hi, I’d like to change window AC unit to a new one. The old one I’m using is 5,200 BTU and it’s not cold enough for summer and now it fails to work properly. My room size (long shape / Studio with kitchen) is 32×11 ft. ( 350 sq.ft.) with 8 ft ceiling, highly sun exposure side of the building (3 windows size: 3×5.2 ft ). I have 2 choices of AC 8,000 BTU or 13,000 BTU. ( someone has extra AC and offer 1 from these 2 to me).

    Which ones should I use? Consider from my information.

    I’ve checked online, it recommended 8,000 btu but with my room size & conditions(very sunny), some website said I should consider to add more BTU than a regular BTU calculation. I’m aware if I use 13,000 BTU, It probably cold more than enough but I concern about electricity bill.

    Normally, I use 20″ portable fan to help the air circulation for AC as well.

    Thankyou so much.

    • Hello Pond, your dilemma is understandable. An average 350 sq ft room would need a 7,000 BTU unit. However, the 3 big windows can really increase the size of the air conditioner you need.

      Of the two choices, 8,000 BTU would be the optimum one. It’s a big increase from 5,200 BTU and it will probably be much more cost-effective than 13,000 BTU device. The rule of thumb is to buy an AC unit that’s a bit bigger than what you actually calculate; in your case, that would be something like a 10,000 BTU device. However, if the choice falls between 8,000 BTU and 13,000 BTU, an optimistic view is that 8,000 BTU should do the job well without increasing the electricity bill significantly.

      • Thankyou very much for your suggestions and ideas. The 8000 BTU will be my final choice.

        I am also thinking to add window films like reflective one to help cut down the sunlight and the heat.

        Thankyou so much again!

  14. Hi
    I am living in the Caribbean, my entire house is 30 * 20 ft, one bed room is 11 * 9 ft floor to ceiling throughout the building is 9 ft. The house is elevated and has wooden floors now can you advise say if i should buy the 4000 BTU for my room or splurge and buy the 12,000/14,000 BTU for the entire house?


  15. I have a lanai 200 square feet with aluminum enclosure and acrylic windows. What size portable AC would work? In the summer here central Florida the room fells like an oven!

  16. Hi, I’m looking to replace a window air conditioner for a 240 sq ft living room with 8 ft ceiling and average sun in Connecticut. The room has a 48 in open doorway to a 90 sq foyer (directly opposite the window with the AC unit) and a 30 open doorway to a 200 sq ft dining room (to the side). The current 8,000 BTU unit does not cool the living room sufficiently. Could I go with a 10,000 or 12,000 BTU unit? Or do I need to get another unit for the dining room (which I’d prefer not to do, as I’m mainly looking to cool the living room)? Thanks for the advice!

    • Hello David, in most cases 8,000 BTU should be more than enough for a 240 sq ft room. However, in your situation with a big window area, the 8,000 BTU unit might struggle to achieve the required temperature. It’s better to be safe than sorry; given the high overall window area, the 12,000 BTU device would be a safer choice.

  17. It is so kind of you to field these questions.

    Here are the specs of my apartment:
    Ceilings: 8.5′
    Central hall area: 8′ x 5′
    Rooms off each side of the hallway:
    Living room: 13′ x 15′ (very warm—southern exposure, over the building boiler room)
    Kitchen: 9′ x 13′ (northern exposure, but warm because of the gas stove)
    Bedroom: 12′ x 12′ (northern exposure)
    Bathroom: 8′ x 8′ (northern exposure, I don’t bother to cool it)

    Up to now I’ve had window units in both the living room and the bedroom. A friend is suggesting that it’s possible to cool this kind of layout with only one window unit (which room?) & good fans strategically placed. I have my doubts. What do you think?

    Thank you!

    P.S. I live in southwestern Connecticut. Humidity is high and in recent summers the temperatures are sweltering for 6-8 weeks.

    • Hello Meg, the total area to cool down is 560 sq ft. According to the EPA, you would have to multiply that number with 20 to correctly size your air conditioner unit. Of course, other factors such as sun exposure and your location can significantly increase the size of the AC unit that would be most appropriate.

      Your friend is right. A 15,000 BTU or 18,000 BTU device could theoretically cool down the entire apartment. The fans are also useful in order to distribute the cooled air throughout the apartment. What size are the 2 window units that are currently installed?

      • Hello again,

        The living room unit is 6,500 BTU and the bedroom unit is 6,000 BTU. I use them only for those rooms. The BTUs are more than adequate for the spaces, but the units are too old to work properly and need to be replaced.

        The configuration problem I anticipate with using a single unit for the whole apartment is that the air flow from bedroom to living room involves passing through a narrow doorway and make a dog-leg turn. I look on fans as efficiency boosters, not as mandatory links in the cooling chain, if you see what I mean. Nor do I want to end up blasting the AC in one room but still getting an inferior result in the other.

        Cooling the living room and the kitchen as one consolidated space is a much easier proposition. Until this summer, I haven’t minded having a hot kitchen. But with the need to work from home now, it would be a huge benefit to have another fully habitable room.

        I’m investigating the Midea U Inverter window units because the position of the compressor should make for quieter functioning. They get excellent reviews, and the sturdiness of the mounting looks like it might save wear and tear on the units, given that I must install and uninstall them every year. Amazon has them in 8,000/10,000/12,000 BTU models.

        Here’s what I’m thinking now. Get two air conditioners. A less powerful one just for the bedroom, a more powerful one to handle the two hottest rooms (living room and kitchen) together.

        I need to keep an eye on the finances, but this is an infrastructure upgrade. 🙂 I’d like to get it right the first time and not have to think about the AC for another ten years!

        Thanks again for helping me to think this through!

        • Thank you for the insight; I’m sure it will be most helpful for everybody who is experiencing similar problems. In short, the logic you’re using is very sound, you know exactly what you’re talking about. Have a cool summer!

  18. Considering this is for a normal housing with wood structure. You should add a concrete duplex/apt for wall units and how much BTU is needed.
    I live in a concrete duplex my bedroom has a wall unit that is small and doesn’t cool at all. bedroom gets full sun all day, and at night the bedroom feels like a stone oven, there is no reprieve.
    The wall ac just died since it is 13 years old and landlord isn’t going to replace it, so, it is up to me, but all i see are window ac units and 5,000btu is too big for the wall opening.

  19. Hi,

    First of all, thank you so much for this website, it has so much useful information and I’m sure everyone who comes across it appreciates it very much.

    Here’s my question; I see that adding a kitchen to the analysis greatly increases the BTUs. For example, when I put in the specs for my apartment, 32 ft by 15 ft, 8 ft ceiling and heavily shaded, the BTUs come out to a little over 10,000. However when I checked off kitchen, it jumps up to over 14,000. Is that extra 4000 BTUs necessary whether or not the kitchen is actually being used? I am no cook and, except for using my microwave and toaster every everyday, I hardly ever use my kitchen except to go to the refrigerator to get something to drink or find something to heat up in the microwave. Is there something about the mechanics of the kitchen that will automatically necessitate an increase of 4000 BTUs or is there an assumption that the kitchen is actively being used, i.e. the oven is being used everyday.etc.

    Again, thank you for maintaining this website.


    • Hello Scott, thank you for your kind comment. The question is very on point; a rule of thumb is to add 4,000 BTU for the kitchen because people who have kitchen usually use it (kitchen appliances, oven, stove, even fridge all create surplus energy). There is nothing in the nature of the kitchen itself that would call for a more powerful air conditioner. If you don’t use your kitchen, you can forget about that 4,000 BTU. The BTU calculator is made with presumption that +90% of people use the kitchen regularly; hence the increased air conditioning demand.

  20. Hello,

    I am looking into installing a mini split but don’t know how big to get it. My kitchen is open to the living room with an attached hallway. I have a total of 5 windows. Kitchen is 17.5 X 8 living room is 16.5 X 12.5 and hallway is 17.5 X 3. All open and connected to each other. Please can someone help.

    • Hello Miguel, the square footage of the kitchen, living room, and hallway combined is about 400 sq ft. The minimum size of the mini split unit for 400 sq ft would be 8,000 BTU. However, for kitchen most HVAC experts add 4,000 BTU because of all the cooking, baking going on. Another thing you need to take into account is the length of the hallway; it’s 17.5 ft long. You might want to get an additional fan in order to create indoor airflow that will distribute the cool air evenly, even as far as the end of the hallway. All in all, 12,000 BTU mini split air conditioner would make a whole lot of sense in your situation.

  21. Hi, i have a tiny shed of 12′ x 32′ 8′ ft in height. But there is a wall in between, one room is 12′ x 18′. The other is 12′ x 14′,what would you recommend for less energy used. Any help will do thanks Manny

    • Hello Manuel, you would need an 8,000 BTU air conditioner. If there is a hole in that wall, the air-conditioned air will reach both rooms. If the wall doesn’t have a hole, you should opt for the smallest portable AC units. You can easily put it in the 1st room and then in the 2nd room. The smallest capacity for a portable AC unit is 8,000 BTU, you can check other small air conditioner choices here.
      For minimum electricity expenditure, look for AC units with a high EER rating (above 10). Hope this helps.

  22. I’m trying to figure out the BTU size for a mini-split I want to put in an addition to augment the central air. The room is 12 x 19.5 with an open ceiling 12′ high at the peak and 7.5′ high on the east & west sides. It attaches to the rest of the rancher thru a 6′ x 6.5′ opening where a patio sliding door used to be. That door is now on the west wall of the addition, The south wall has two 5′ tall x 4′ wide casement windows on either side of one centered 5 x 6 bay window. Then there is a 5 x 5 casement on the east wall.

    • Hello Bob, the space-wise structure you have there is quite complex. You should probably talk with an HVAC installation expert who can also recommend the best mini split to use, in addition to AC capacity (BTU). We have 1000s of experienced HVAC expert across the US, you can use this link to get an HVAC expert in your area to help you out. They’ll certainly know how to calculate that ceiling slope.

  23. Hello, I am trying to get an AC unit for my fifth-wheeler. It’s 32×9 in average (somewhere in between 280-340 sqft). The ceiling has a height of 8 ft. Do you think a 15,000 BTU unit would be an overkill? Also, I am considering that since it is pretty long (32 ft) 15,000 BTU could do a great job. Thank you

    • Hello Julio, for 280-340 sq ft, 15,000 BTU would be an overkill. You’re correct to be concerned about the 32 ft length; you want to have a conditioned air throughout the fifth-wheeler. The best solution here would be a 10,000 BTU unit with a strong airflow. Strong airflow – something above 300 CFM – is better for long spaces because it can push the air along the space much better.

  24. interesting problem with the Midea U-shaped inverter unit. As great as it is, unfortunately, it cannot be left in the window during cold winter. Midea owners manual (and Midea comments on Amazon) recommends that the unit be taken out and stored for winter. I confirmed this with Midea directly, and they said the “sensor” could be damaged by extreme cold, so its not even a case of shortened life expectancy. I suggested that most people in cold climates never remove their window units, especially heavy 10k BTU models. This is especially true for apartment dwellers, who also have no place to store big AC units. I fear that Midea will get lots of warranty calls next summer when these units fail. They will also lose lots of sales when people in cold climates realize they can’t leave them in window all year. Hopefully they can fix this.

    • Hello Jeffrey, thank you for the insight. Normally, it’s recommended to remove any window AC unit during the winter. There are two reasons for this; window AC units don’t isolate from the winter weather as well as windows and most homeowners like the improved aesthetics when they tuck the unit away for the winter (not the most appealing device to have on a windowsill). Furthermore, this will also increase the unit’s lifespan. So, all in all, it makes a lot of sense to pack any window AC unit away for the winter; it’s not actually a problem, it’s a well-thought-out recommendation.

  25. Hello.
    I just bought a little single wide in Texas. 2- 130ft sq bedrooms 1- 48sq ft bathroom, living room and kitchen 338 sq ft and ceiling is 7 ft. I am thinking of buying a mini split. Is it possible to just use one console to heat/cool the whole place? If yes, how many btu’s do you reccomend?

    Thank you:)

    • Hello Jessica, you’re looking to heat/cool about 700 sq ft, divided among 4-5 rooms, including a kitchen. You would need about 20,000 BTU device, or even a bit more. You’re correct; a mini-split heat pump is a perfect choice for your situation (just with 1 console). You can check out a number of the best 24,000 BTU mini-split heat pumps here, and read about how energy efficiency specs (SEER, HSPF) affect the electricity costs in the long-term.

  26. Hello! I just want to start out by saying this is an awesome website and super helpful.
    I have a 1050 sq.ft garage with 9 ft ceilings and no divided spaces. I plan on installing a 2.5 ton system, with 2 total head units, one on either side of the room to evenly circulate airflow through the large space. It is insulated very well with decent heat load as I live in California. I am just wondering if this should be sufficient for the space I’m trying to cool.

    • Hello James, thank you for the compliments. You have the right idea about the placements of the 2 head units; a 2.5-ton system will be enough for properly cooling your garage.

    • Hello Tommy, if we apply the EPA recommendations for 8 ft ceiling we get 640 sq ft * 20 = 12,800 BTU. Now, 18,000 BTU would definitely do the job but it might be an overkill. According to the calculation, the 12,000 BTU is nearly enough. Basements tend to be colder because they have less sun exposure and are located near the ground. 12,000 BTU might just cut it, especially if you have a 7 ft ceiling.

  27. I’m confused. I was informed my 10,000 BTU portable AC unit was not cooling my apartment’s front room, kitchen, hallway, total 380 square feet, because a 8,000 BTUs unit would be better. I have 3 large, sun drenched windows in the front room. The ceilings are 8 feet.

    • Hello Missy, 8,000 BTU is the optimum capacity. The 10,000 BTU would be overkill; it would cool the space better due to 2,000 BTU more cooling power but the electricity bill and the initial portable AC cost would be higher.

  28. Hello, my ac person recommends i put in a 12000 ac/heat system fujitsu, in apartment that has the following, living room = 225 sq/ft, master = 210 sq/ft, bedroom2 = 201 sq/ft, bedroom3 = 126 sq/ft, kitchen = 198 sq/ft entrance(common area between all rooms) = 97 sq/ft, all rooms have doors, for total of 1057 sq/ft TOTAL, 8ft ceiling height and he says that will be enough because not open concept, my question is, will the whole apartment feel cold, or some rooms maybe be hotter if I get it, will it be rushing or is 15 or 18 btu system overkill and cost wise will it be much more expensive to purchase and run day in and out, thank you for your time and help

    • Hello Walter, the basic EPA recommendation is that you would need 20 BTU for every sq ft. 1057 sq ft would, using this recommendation, need 21,140 BTU unit. The 12,000 will cool down a few rooms (living room + master + bedroom 2, for example) but not the whole apartment. You have to close the door somewhere in order to create a 500-600 sq ft isolated area.

  29. I am building a small L shaped home. One part is 48×20 that has the living room & a small office area, 3 bedrooms, 2 bathrooms. The other part is 20×16 open kitchen/dining area. How climate is mostly in the 80s year round and very humid (Hawaii problems😉) What air cooling system would you recommend. I’m also on a tight budget. Thank you for your help

    • Hello Charlie, you would need about 30,000 BTU, maybe a bit more (Hawaii problems :)). Because you have the L shaped home with a number of rooms, you’ll need a number of units. The best option are the 3-zone mini-split units; you get 1 outside unit and 3 indoor air handlers you distribute evenly around the house.

      If you check those 3-zone mini-splits, you will see that the best one – with 36,000 BTU – is Senville SENA-36HF/T. That’s the most budget option you can get; it also has high energy-efficiency which means low running costs. Hope this helps.

  30. I’m looking at installing split system. My house is 4 bedrooms plus lounge/ dining and family/kitchen just wondering how many systems and what size( was advised by store that I would need 1 for each bedroom and possibly 2 others) Expensive!! But not sure if this will be correct??

    • Hello Tracy, for a big house with big rooms (bedroom, 2 other rooms), you can buy a multi-zone mini-split system. They can be quite expensive; a 3-zone mini-split with 3 x 9,000 BTU can quickly cost as much as $5,000. You can check the LM’s article about the best 3-zone mini-splits here to check for the most optimum units.

  31. My girls just moved into a small 2 bedroom house without ac. We need to decide on portable ac or a window unit.

    the living room and kitchen are next to each other and the 2 bedrooms are down a average size hallway.

    Living room is 17×12, kitchen is 10×15 and bedrooms are 10 x 13 and 11X15

    if the ac unit is placed in a window that faces the hallway and in between kitchen and living room, will the air conditioner cool the hall and the bedrooms too? luckily my girls unit, utilities are included.

    Also I love your calculator. In most literature I see it measured by square footage per room and that it wont cool anymore than that and it wont cool correctly if unit is too big for that room. this confuses me.

    I just need to know what size to get and where it is best to place it…

    • Hello Joy, thank you for your kind words. Between portable and window AC, it’s always best to buy a portable unit because you can move it around and find that perfect spot (on the hallway, for example). A window unit is always in 1 room and can’t be moved – if you put it in the living room, will the bedrooms be covered as well? These are the kind of issues you get with window ACs.

      The total square footage is about 650 sq ft. Normally, you would need a 13,000 BTU unit for that. If you account for hallways, a 15,000 BTU portable AC unit placed on the hallway between the rooms might be the most optimum option. For 18,000 BTU+ unit, you’ll need 240V voltage, keep that in mind if you decide on a bigger unit. You can check some of the best portable ACs with a high-efficiency rate here.

  32. If I’m living in Florida and have 14,000 btu ac how cold will that keep the room if its 90 degrees and the room is 12×10 and there 9 feet high ceilings

    • Hello Karl, sufficiently cool even in Florida’s heatwave. That’s a very small room and quite a normal-sized air conditioner. You can set the temperature as cold as you wish; the 14,000 BTU AC will handle it.

  33. Hello…I live in Mesa, Az and want to install a Mitsubishi mini-split for my garage.
    I want to be able to cool the garage down to 80 to 85 degrees from 100 to 110 degrees outside temp. 3 car garage, 9 foot ceilings, 660 square feet with one window…walls, ceilings and garage doors insulated…. is 18,000 BTUs enough?

    • Hello Marc, the conservative estimation by EPA is ’20 BTU per sq ft’; that’s for living areas, 8-foot ceiling, standard insulation, and so on. Even in those conditions, the safer way is 25 BTU per sq ft. For a 9 foot garage, 30 BTU per sq ft might be more appropriate. 660 sq ft * 30 BTU per sq ft = 19,800 BTU. With 1 window, good insulation, 18,000 BTU might just be enough, yes. You can check some of the air conditioners appropriate for the garage here, maybe it could help a bit.

  34. This subject can be much more complicated….
    My room is 16.5’x 9.6 with ceiling sloped from 7’ to 8’ . So let’s say 7.5’
    It has 3 windows that are roughly
    The roof is a very slight slope-almost a lean-too. So not much for attic space.
    It is a audio room / bedroom.
    So I have the heat load of the equipment to also consider.
    It is on the west side of house as well.
    I am also in central Texas!
    I have a 10,000btu window unit in there now that is just enough, but way too noisy. I have window coverings that are insulated.
    What do you recommend for a mini-split for 120v with no heat and is whisper quiet?
    Thank you
    It only

  35. Hey. I have 1000 sq foot house. Currently a small unit in living Room . on other side of the house with the bedrooms were unbearably hot and humid this past summer. Is it best to replace the one unit with 20000 btu’s or two smaller units since cooling multiple rooms?

    • Hello Selena, 20,000 BTU unit has the right size, and will deal both with hot and humid indoor air. However, 15,000+ BTU units require 220V voltage. If you will have to upgrade your electrical grid just for that, it might make more sense to buy an additional 12,000 BTU or 15,000 BTU unit. Together, they will also create a more homogenous cooling (without hot spots); this might be a problem with 1 20,000 BTU unit if it has a low airflow (measuring in CFM).

  36. Your site has given me a lot of ideas… but not fully addressing my specific need. I live in Southwest Florida and have a 12 x16 lanai with 8-1/2 foot ceilings that receives the sun most of the day. There are shaded non-glass windows (tax reasons) on two of the four walls. In order to maintain a reasonable comfort level, what size thru-the-wall A/C unit would you suggest? Thanks

    • Hello Ray, 12*16 is 192 sq ft; with a bit over 8 ft ceilings. In a normal situation, a 6,000 BTU would suffice. Add Florida, sun exposure, big non-glass windows to the equation and you’re looking at 10,000 BTU unit (just to be safe). You can check out the LG unit in our list of the best thru-the-wall AC unit.

  37. Hello, I’m looking for a solution for our new house with casement windows.  Ultimately, I know a mini-split system will be best, but it’s out of our budget right now.  So, we’re looking at getting several portable units with plexiglass window covers (with cutouts for the exhaust).  The master bedroom is on the 2nd floor, 425 sf, including the bathroom.  Mostly 8′ ceilings with one peaked area up to 12′.  I’m assuming a 12,000 or 13,000 BTU unit.  Another bedroom is 160 sf, so I’m assuming an 8,000 BTU unit.  We probably won’t run this one unless we have guests.  Now here’s the fun part- an open concept area with the living room, dining room, kitchen, plus the hall, laundry room, a half bath, and a full bath.  That area is about 900 or 1000 sf, with many windows and a cathedral ceiling in the living room up to 25 feet or more.  I’m thinking 3 units- one in the living room, one in the laundry room doorway in the hall (aimed at the kitchen), and one on the upstairs landing above the living room.  But I don’t know what size I’ll need for those 3 units.  Any advice?  Anything we need to be aware of for electrical systems?  Or single vs dual hose units?  We’re in the northeast US.  Thanks for your help!

    • Hello M, nice plan. Your calculations for the master bedroom with bathroom and another bedroom sound about right. The cathedral ceiling open concept area is fun indeed. 🙂 Calculating the full volume of that area is a bit complex. Let’s simplify it a bit; a 1,000 sq ft area with 16 ft average ceiling height. For that you would need somewhere between 40,000 and 50,000 BTU; depending on insulation, sun exposure, and so on.

      Portable units running of 110/120V go up to 15,000 BTU (above that, you’ll need 220/240V voltage). Obviously, dual hose units are better (higher efficiency, lower long-term costs; based on EER rating).

      3 14,000 BTU dual hose air conditioners will give you a combined cooling output of 42,000 BTU. That just might be sufficient given your in the northeast US; your calculations are again on point. You might want to check out our article about the best dual hose portable air conditioner here; you will find very efficient 12,000 BTU and 14,000 BTU units with a very good reputation.

      Overall, you do have a remarkably good eye for these BTU calculations and the general layout of portable AC units. You’ve got this solved.


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