Mini Split Btu Calculator – What Size Ductless AC/Heat Pump Do I Need?

What size mini split do I need? How many BTU should it be?

Those are common questions, but there isn’t a super-simple answer.

Mini split size for your home depends on these key factors:

  • Where you live
  • Whether you need just AC or heating too
  • The size of your home

We’ll clearly explain all this, so you’ll be able to determine the right size mini split AC or heat pump for your home wherever you live.

Mini Split Heat Pump Calculator / AC Calculator

Want a Quick Answer to Mini Split Sizing?

Use our Mini Split AC and Heat Pump BTU Calculator! The details are explained below, but you can get started toward the answer to mini split BTU sizing right here.

Steps to follow are found under the US Climate Zone Map and the Calculator.

Read the information below the Calculator. Why? There is very important information on whether to choose the AC or Heat Pump Calculation based on where you live and what HVAC equipment you might currently have, so please check it out.

Mini Split AC/Heat Pump Btu Calculator

1. Locate the Zone you live in.

2. Enter your home’s square footage. It can be determined by adding the square footage of each room (multiply length x width) and adding them. It will also be found on a blueprint or house drawing or in advertising/closing documents from when you built or bought the home.

3. Insulation Condition

  • If you’ve upgraded the insulation and window/doors for energy efficiency, choose Good.
  • If the home was built after 2000, choose Average or Good.
  • If the home was built between 1980 and 2000 with no insulation upgrades, choose Average or Poor
  • If the home was built before 1980 with few upgrades, choose Poor

4. Sun Exposure

How much sun hits the house? Consider especially how sunny the house is in the afternoon, when sun and heat combine to make a home very warm and cause the AC to work hard.

5. Mini Split Type – AC or Heat Pump

OK, this is where a couple pointers will assist you in getting the right answer to, “what size mini split do I need?”

Do a calculation for both heat pump and AC. This is crucial to getting the right answer. You’ll see differences in recommended sizing, especially in zones with extreme weather (e.g., Zones 1, 2, 6 and 7).

In Zones 1, 2 and 3, the warmer zones, use the AC calculation even if you plan to install a heat pump that provides both air conditioning and heating. If you try both, you’ll see that the heat pump rating isn’t nearly as high as the AC rating, because in warm climates, a lot less heat is needed. But a lot more air conditioning is required to keep your home comfortably cool and dehumidified.

In Zones 6 and 7, use the Heat Pump calculation for the opposite reason – you’ll need a lot more heat than AC in those zones.

Exception to the Rule: What if you live in a cold zone and have a furnace or other source of heat such as a standard boiler or a wood boiler or furnace?

If you have a reliable source of heat already and are planning to add a mini split air conditioner, then, of course, just use the AC calculation on the Mini Split System BTU Calculator.

What Size Mini Split ACs and Heat Pumps are Available?

Most mini split, aka ductless heat pumps and ACs, are available from about 9,000 BTU to 48,000 BTU, but larger sizes are offered in a few select brands and series.

BTUs to Tons – If you’re familiar with standard split system sizing, then sizing by tons instead of BTUs might make more sense.

1 ton equals 12,000 BTUs. So, converting the BTU rating to a ton rating, here are the most common split system sizes.

K=1,000 BTUs

BTU Rating

Ton Rating

9K

0.75

12K

1

18K

1.5

24K

2

28K

2.333

30K

2.5

36K

3

42K

3.5

48K

4

In short, divide the BTU rating by 12,000 to get the ton rating.

What Size Mini Split Do I Need?

If math isn’t your strong suit, this section might be useful.

It will assist any reader in knowing the general size requirements for different zones or areas commonly found in homes – maybe a home like yours. It answers common questions we receive:

  • What size mini split for bedroom?
  • What size mini split for living room?
  • What size mini split for garage?
  • What size mini split for apartment?
  • What size mini split for 500 square feet?
  • What size mini split for 1000 square feet?

Chart of Recommended BTU Per Square Foot

Room/Area Size

Examples

Recommended BTU

100-350 sq ft

Den, office, small bedroom, 1-car garage

9,000

350-500 sq ft

Studio/1-bedroom apartment, 2-car garage

12,000 (1 ton)

500-700 sq ft

Small 2-bedroom apartment

18,000

700-900 sq ft

1 or 2-bdrm townhouse, cottage

24,000 (2 ton)

900-1,100 sq ft

2-3 bdrm apartment or townhouse

30,000

1,100+ sq ft

3- bdrm townhouse, home addition

36,000 (3 ton)

Mini Split Sizing Tips by Room

A 12,000 BTU AC might be perfect for a 400 square foot bedroom suite but too small for a kitchen. Why? Because the kitchen gets quite warm when the oven is on at 350 degrees while dinner cooks. Appliances add heat. Even a refrigerator adds heat because it removes heat from inside the unit and exhausts it out the back.

So, here are a few tips for sizing a mini split heat pump or AC in various rooms or zones of the house.

Bedrooms – Know your sleep style. If you like it really cool in summer, or if you hate covers and still want to be warm in winter, then choose a unit that is 6,000 to 12,000 (but no more) larger than the calculated size.

Kitchens – As noted, go a size (6K-12K) bigger, so you can have enough air conditioning power to keep the room cool when the range, stovetop or other food prep appliance is working.

Living and Family Rooms – These are gathering locations in many households. More people (@98.6 degrees each) mean a lot more heat. You might want to boost your mini split AC size by 6,000 BTU.

Rooms with Vaulted Ceilings – Also called sloped and cathedral ceilings, these structures allow heat to rise up and out of the living space. As a result, you might want to select a heat pump size about 6K to 12K more than calculated.

Here’s another, more energy-efficient, solution for rooms with very high ceilings – Install a ceiling fan. The fan pushes air downward in summer to provide a cooling breeze. Flip the switch to reverse fan blade rotation in winter, and it pushes air up, forcing the warm air accumulating at the ceiling to flow down the walls and back into the living space!

You’ll cut energy costs with a ceiling fan whether you are heating or air conditioning the room! However, reducing energy use is only possible when you adjust your thermostat – setting it higher in summer and lower in winter. A ceiling fan allows you to do this and remain just as comfortable. Learn more in this Energy Saving Guide from Pick HVAC.

Note on Mini Split for Garage Installation

Mini Split for Garage

For gr installation, consider that most garages are poorly insulated. When you use the Mini Split System Size Calculator. If there is no insulation in your garage – or just in the ceiling but not the walls, then definitely use the Poor setting for Insulation.

And then boost your BTU requirement by at least 12,000, because you’ll need that extra heating and/or cooling in a poorly insulated garage. In winter, heat easily escapes. In summer, heat transfers through the roof, walls and door to make it very warm inside a garage.

Here’s an example, but of course, you might prefer to use your own variables for Garage Size, Zone and other inputs to make your calculation.

  • Zone 3
  • 572 square feet (for 2-car garage approximately 22x26)
  • Poor insulation
  • Average sun exposure
  • Air Conditioner

The result is about 12,000 to 15,000 BTU.

But we’ll tell you right now that even a 15,000 BTU mini split AC isn’t going to do the job on the hottest days in a poorly insulated garage.

Our recommendation would be to choose something in the 24,000 to 32,000 BTU range (2 ton to 2.5 ton units).

In colder zones, you’d want to select Heat Pump instead of AC, and then add another 12K to 18K BTU to the calculation.

Why is Mini Split System Size so Crucial

Installing a properly sized mini split heat pump or air conditioner ensures that your home is comfortable without wasting energy.

Heat pumps: A heat pump provides heat and air conditioning. When in air conditioning mode, it removes both heat and humidity from the air. Dry air is more comfortable at a higher temperature, so you can set the thermostat 2-4 degrees higher, save money, and enjoy a pleasant indoor climate.

Isn’t a heat pump oversized for heat if it is properly sized for AC? If you’re asking that question, you’re onto something. Yes, in South Florida or the Valley in Arizona, you’ll lead plenty of AC to keep the air cool (and remove humidity in FL). If you need 48,000 BTU of air conditioning in those places, proper sizing for a heat might be half that – about 24,000. An opposite scenario is found in colder zones.

In fact, if you play around with our Mini Split BTU Calculator, that’s what you’ll find.

Zone 1 – 2,000 square foot home: AC needed is 48,000 to 60,000 BTU (if using the ton rating, it is 4 to 5 tons). The heating requirement in the same home in the same location is just 24,000 to 32,000, or almost exactly half.

Zone 7 – 2,000 square foot home: AC needed is 24,000 to 32,000 BTU while the heat needed is about double, 48,000 to 60,000 BTU.

That is why in Zones 1-4, you should use the AC rating in the Calculator even if buying a mini split heat pump. And in Zones 5-7, you should use the Heat Pump rating.

Still Unsure?

We hope this information helps you narrow down the size of the mini split system you need. This is especially useful if you are planning DIY mini split installation using one of the brands that makes pre-charged systems that do not require pro installation. 

However, if you still have questions, we can assist you in getting your questions answered and getting free, no-obligation written quotes from pre-screened, insured installers in your area. Choose the Free Local Quotes tab or call the number at the top of the page, and you’ll have convenient and free mini split system recommendations and estimates very soon. 

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