How Many BTU Air Conditioner Do You Need? (+ AC Size Calculator) (2023)

What size air conditioner do I need?

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):

How Many BTU Air Conditioner Do You Need? (+ AC Size Calculator) (1)

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

(Video) How Many BTUs Do I Need? How To Properly Size A Room Air Conditioner |

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

There are only 2 rules:

  • Not too big. Obviously, you don’t want a 14,000 BTU window air conditioner for a small 12×12 room because it unnecessarily boosts your energy bill.
  • Not too small. You don’t want to get hot in the summer because you bought a 6,000 BTU portable air conditioner for a 1,000 sq ft apartment.

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

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.

How Many BTU Air Conditioner Do You Need? (+ AC Size Calculator) (2)

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 tiny12×12 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.

(Video) How to Figure What Size Air Conditioner Will Cool a Room : Air Conditioning

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

Example: How many BTU do you need for a 20×20 room? For a 20×20 room, you need about 10,000 BTU of cooling output.

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.

(Video) air conditioner tonnage calculation : how to find air conditioner size

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

BTU = Square Footage× 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.

(Video) How to calculate room air conditioner size | AC calculation | Earthbondhon

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.

For smaller spaces (example: camping air conditioners for tents), you can use portable battery-powered AC units.

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

  • Mini-split AC units. Example: Mr Cool mini-split units have the highest SEER rating of above 20 EER.
  • Portable air conditioners. Here you can check the biggest (up to 15,000 BTU), quietest (below 50 dB), and portable AC with heater units. These are the best portable AC units for apartments, for example.
  • Window AC units. Here you can check the biggest (24,000+ BTU), quietest (below 42 dB), and window AC units with heaters. Special kinds of window AC units include casement window AC units, through-the-wall AC units, saddle window AC units, and low-profile window units.

Note: Evaporative coolers and mini personal air coolers do not produce a cooling effect that can be expressed in BTU. They use water evaporation instead of the refrigerant-based system to provide a cooling effect.

You can also check a similar BTU calculator for heating here.

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.

Related posts:
  1. 10 Types Of Air Conditioners Explained (With Pictures, Prices)
  2. How Do Portable Air Conditioners Work? (Easily Explained)
  3. How Much Does It Cost to Run An Air Conditioner? (Cost Calculator)
  4. How Big A Generator Do I Need To Run A 5000 BTU Air Conditioner? (Calculated)
  5. Best 5 Zone Mini Split Systems In 2023 (Mitsubishi, Carrier, etc.)
(Video) How to Calculate Room Area For AIR Conditioner | AC Size According to Room Size


How do you figure out how many BTUs you need in your AC? ›

The Rules for Keeping Cool

As a general rule, an air conditioner needs 20 Btu for each square foot of living space. But other considerations, such as the ceiling height and the size of your windows and doorways, might call for more cooling power. To measure your room, multiply the length by the width.

How many square feet will a 12000 BTU air conditioner cool? ›

12,000 BTUs will cover 400 sq. ft. (3,200 cubic feet) 13,000 BTUs will cover 450 sq.

How many square feet will a 10000 BTU air conditioner cool? ›

Specifically, an 8000 BTU air conditioner can cool a 300-400 square foot room, while a 10000 BTU air conditioner can cool up to 500-700 square feet.

What happens if BTU is too high? ›

A unit with too many BTU's, will cool the room fast, but leave the room humid. Too few BTU's will never cool the room down and the unit will run incessantly.

How many square feet will a 8000 BTU air conditioner cool? ›

At 8,000 BTU, it has the cooling capacity for up to about 350 square feet.

What size room will a 15000 BTU air conditioner cool? ›

Air conditioners rated at 15,000 Btu should be enough to cool most rooms up to about 875 sq. ft.

What size room will a 18000 BTU air conditioner cool? ›

LG 18,000 BTU Window Air Conditioner, Cools 1,000 Sq. Ft. (25' x 40' Room Size), Quiet Operation, Electronic Control with Remote, 3 Cooling & Fan Speeds, ENERGY STAR®, Auto Restart, 230/208V.

What size air conditioner do I need for a 1200 square foot home? ›

If you have a 1,200-square-foot home, you'd need a two-ton unit. A 2,400-square-foot home would need a four-ton unit. Again, there are 2.5-ton and 3.5-ton units in case your square footage doesn't work out perfectly for a two- or three-ton unit, for instance.

How big of an AC do I need for 2000 sq ft? ›

If your home is 2000 square feet, you can calculate your HVAC needs the same as you would for a 1600 square foot home. Assuming one ton of cooling capacity can cool 400 square feet of your home, you'll need about 5.0 tons of air conditioning capacity. Multiply this by 12,000 BTUs, and you'll get 60,000 BTUs.

What size AC unit do I need for a 2400 sq ft house? ›

The answer to the question, “what size AC unit for 2400 square feet?”, would be, is 60,000 BTUs or 5 Tons. It's possible to fall between unit sizes, so if that's the case with you, then you should choose the next higher size.

How many BTUs do I need for 1200 square feet? ›

1,200 square foot home would take between 35,000 and 75,000 BTUs. 1,500-square-foot home would take between 45,000 and 90,000 BTUs. 1,800-square-foot home would take between 55,000 and 110,000 BTUs. 2,100-square-foot home would take between 65,000 and 125,000 BTUs.

Is the higher the BTU better or worse? ›

BTU basics

A measure of an air conditioner's power is its BTU rating. BTUs are the energy used to remove heat from a room. Therefore, the more BTUs an air conditioner unit has, the better equipped it is to cool a larger space.

Can you go too big for AC unit? ›

Air conditioners that are too big consume more energy, endure more wear and tear, and simply don't work as well or as long as an appropriately sized unit. This can cause higher utility bills, more repairs, and discomfort in your home.

What size air conditioner for 1500 square feet? ›

What size air conditioner do I need for a 1,500 square foot house? A 2.5 ton air conditioner is best because about 30,000 BTU is needed for a house that's 1,500 square feet.

Is it better to oversize or undersize AC? ›

Better to oversize or undersize ac

However, in general, it is better to slightly undersize your AC unit than to slightly oversize it. If your AC unit is too small, it will have to work harder to cool your home, which can lead to increased energy costs and a shorter lifespan for the unit.

How do I know if my AC unit is too big? ›

Here are four classic symptoms of an oversized unit:
  1. High Humidity. Oversized units don't run long enough to dehumidify indoor air. ...
  2. Short Cycling. Because it's so large, an oversized AC meets your home's cooling load in ten minutes or less and then cycles off. ...
  3. Hot and Cold Spots. ...
  4. Shorter Lifespan and Higher Utility Bills.
Apr 18, 2018

Can an air conditioner have too much BTU? ›

Generally speaking, a higher BTU is not better for your AC system. That's because higher BTUs will make the room more humid. It will also put more wear and tear on the unit, requiring more maintenance and shortening its lifespan.

Does higher BTU mean more electricity? ›

One BTU is the amount of energy it takes to raise one pound of water one degree Fahrenheit. The higher the BTUs, the more power the system has.

Is it cheaper to run a window air conditioner or central air? ›

It depends. If you're looking to cool your entire house, having multiple window air conditioners will use more energy than a single properly-sized central air conditioner would. Conversely, if you need to cool a single room, a window air conditioner will, of course, be the more efficient option.

What size room will a 7500 BTU air conditioner cool? ›

LG 7,500 BTU Window Air Conditioner with Supplemental Heat, Cools 320 Sq. Ft. (16' x 20' Room Size), Electronic Controls with Remote, 2 Cooling, Heating & Fan Speeds, Slide In-Out Chassis, 115V.

How many BTU do I need for 2000 square feet? ›

HVAC contractors use a rule of thumb to allocate 20 BTUS to every square foot of space inside your home. For example, if your room is around 2,000 square feet, you'd require a system with a BTU rating of 4.3 out of 5.

What size air conditioner do I need for 2000 sq ft house? ›

For example, when considering what size air conditioner is needed for a 2,000 square foot home, you would likely choose a 3 or 3.5 ton unit, depending on the climate where you live.

How many square feet will 24000 BTU cool? ›

A 24,000 BTU system will generally heat and cool a space that is around 1,500 sq. ft.

How many square feet will 15000 BTU cool? ›

Air conditioners rated at 15,000 Btu should be enough to cool most rooms up to about 875 sq. ft.

How many square feet will 25000 BTU cool? ›

400 sq. ft

How many BTUs do I need for 1200 ft ²? ›

1,000 to 1,200 ft2: 35,000 to 42,000 BTUs. 1,500 to 2,000 ft2: 52,700 to 70,000 BTUs.

How many BTUs do you need for 1500 ft ²? ›

A 1,500-square-foot home will require between 45,000 to 90,000 BTUs. A 1,800-square-foot home will require between 55,000 to 110,000 BTUs. A 2,100-square-foot home will require between 65,000 to 125,000 BTUs. A 2,400-square-foot home will require between 75,000 to 145,000 BTUs.

What happens if your AC unit is too big? ›

Oversized air conditioners usually short-cycle, meaning they power up and down throughout the day many more times than units that cycle properly. This needlessly uses up energy, resulting in high energy bills for you. Short AC lifespan – An oversized air conditioner is an overworked air conditioner.

How many square feet will a 2.5 ton AC unit cool? ›

- 1500 sf

How big of a room will 18000 BTU cool? ›

700 – 1,000 sq. feet: 18,000 BTUs.

How many square feet will 42000 BTU cool? ›

1,400–1,500 sq/ft = 24,000 BTUs. 1,500–2,000 sq/ft = 30,000 BTUs. 2,000–2,500 sq/ft = 34,000 BTUs. 2,500–3,000+ sq/ft = 42,000–60,000 BTUs.

How many mini splits do I need for a 1500 square foot house? ›

Usually, we use a 20 BTU per sq ft rule of thumb. Example: For a 1,500 sq ft home, you would need 1,500×20 = 30,000 BTU output. You can use one 30,000 BTU mini splits, two 15,000 BTU mini splits, or three 10,000 BTU mini splits.

What is the difference between 12000 BTU and 18000 BTU? ›

For a room of 35-60 square meters – you need air conditioning capacity of 12000 BTU. Those who have a home area of 60 to 80 square meters – require an air conditioner with a capacity of 18000 BTU.

How many BTU do I need for a 20x20 room? ›

How many btu do I need for my room?
Room TypeRoom SizeRecommended BTU
13 x 13 room169 sq ft6,000 BTU
14 x 16 room224 sq ft6,000 BTU
16 x 13 room208 sq ft6,000 BTU
20 x 20 room400 sq ft9,000 BTU
4 more rows
Apr 25, 2022

What size AC unit do I need for a 1600 sq ft house? ›

According to Hunker, “A 1,650 square foot house equates to approximately 3.5 tons. The calculation is based upon multiplying 1,650 by 25 to get the approximate BTU needs and dividing the total by 12,000.” Additionally, a '1,600-square-foot home will generally require a 3-ton air conditioning unit.


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3. BTU Calculations
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