How Many Mini Splits Do You Need? (Rooms, Sq Ft, BTUs, Zones)

“I have a 1,500 sq ft house. How many mini splits do I need?”

This is a standard question about the number of mini splits required. A 1,500 sq ft house would need about 30,000 BTU (2.5 ton) of cooling output; that means you would need 1, 2, or 3 mini splits (we talk about single-zone, 2-zone, and 3-zone mini splits).

how many mini split do i need depends on the layout
Example of a 2-zone mini split system: These 2 indoor air handlers can adequately cool 4 rooms with combined square footage of 1,500 sq ft.

Now, we get a lot of questions regarding how many mini splits you should install. Here are just a few of them (we are going to address and answer all of them further on):

  • “How many rooms can a mini split cool?”
  • “Do you need a mini split in every room?”
  • “How many square feet does a mini split cool?”
  • “How many BTU per square foot for a mini split?”

According to Statista 2016 report, single-zone mini splits and multi-zone (2-zone, 3-zone, 4-zone, 5-zone, 6-zone, 7-zone, 8-zone) mini splits represent 77% share of all air conditioners worldwide. In short, a mini split is the most popular type of AC unit used today, so it’s no surprise that so many people are trying to figure out how many mini splits they need.

To help everybody out how many mini splits you need, we have included a Mini Split Number Calculator and Mini Split Number Chart below. You can consult both of them to get a grip on how many mini split units you need.

how many mini splits calculator
You can find these two useful resources further on.

However, let’s first learn how these multi-split calculations work and answer questions along the way.

Here’s how determining if you need 1, 2, 3, 4, 5, or more mini splits work:

  1. Based on the size of your home, calculate the BTU requirements (primary factor). 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.
  2. Be aware of the airflow and access to different rooms (secondary factor). Matching the cooling output (BTUs) is not enough. If you have a larger space, the airflow from a single 30,000 BTU mini split, for example, won’t be able to flow into all the rooms adequately. You will be left with hot pockets and inhomogeneous temperature dispersion. Having closed doors also prevents the cool air from coming into a closed room.

Based on these two factors, we can quite easily determine how many mini splits you need. We are going to show you how to calculate the BTUs, which mini split indoor handler sizes you can choose from, and how many mini splits you need for how many rooms. Let’s what with the BTUs:

How Many BTUs Do You Need From Your Mini Splits?

When we talk about multi-zone mini splits, this is what we have in mind:

  • 1 outdoor unit. This is where the compressor and all the power comes from.
  • Several indoor units or air handlers. 1 outdoor unit can power 1, 2, 3, 4, 5, 6, 7, or even 8 indoor air handlers. We call this 1-zone, 2-zone, 3-zone, 4-zone, 5-zone, 6-zone, 7-zone, and 8-zone mini splits, respectively. Indoor air handlers can produce anywhere from 9,000 BTU to 3,6000 BTU (3-ton) cooling output.

The first thing you need to do is determine how many BTUs you need. The easiest way to find this out is either to use this AC BTU calculator (gives a more precise estimate) or to use a simple HVAC rule of thumb, stating:

“You need 20 BTU per sq ft of living area (8 ft ceiling height).”

This simply means that you need to multiply the square footage of your home you want to cool by 20 BTU.

Example 1: How many BTU do you need for a 1,000 sq ft house? How many mini splits for a 1,000 sq ft house?

BTU Requirement (1,000 Sq Ft) = 1,000 Sq Ft × 20 BTU = 20,000 BTU

You know you need about 20,000 BTUs. You have to choose between combination of air handlers. Namely, most HVAC producers sell 9,000 BTU, 12,000 BTU, 15,000 BTU, 18,000 BTU, 24,000 BTU, 30,000 BTU and 36,000 BTU units.

In this case, you can go for:

  • 1-zone mini split with 24,000 BTU air handler. This is a bit more than 20,000 BTU requires but it’s better to have a bit more than a bit less.
  • 2-zone mini split with 9,000 BTU and 12,000 BTU air handlers. The combined cooling output is 21,000 BTU; very close to the 20,000 BTU required.

Let’s do another example to illustrate this:

Example 2: How many BTU do you need for a 3,000 sq ft house? How many mini splits for a 3,000 sq ft house?

BTU Requirement (3,000 Sq Ft) = 3,000 Sq Ft × 20 BTU = 60,000 BTU

In this case, we need 60,000 BTU of cooling output. How many mini splits is that? Here are the combinations you can use:

  • 2-zone mini split with two 36,000 BTU air handlers. Total output: 72,000 BTU.
  • 3-zone mini split with two 24,000 BTU units and one 18,000 BTU unit. Total output: 66,000 BTU.
  • 4-zone mini split with two 12,000 BTU units and two 18,000 BTU units. Total output: 60,000 BTU.
  • 5-zone mini split with five 12,000 BTU units. Total output: 60,000 BTU.
  • 6-zone mini split with three 9,000 BTU units and three 12,000 BTU air handlers. Total output: 63,000 BTU.
  • 7-zone mini split with seven 9,000 BTU air handlers. Total output: 63,000 BTU.

As you can see, there are many available combinations. In general, it’s better to use more indoor air handlers than less. This is because of the airflow and homogeneous cooling. Let’s account for that as well:

How Many Rooms Can A Mini Split Cool? (Airflow Factor)

Correctly calculating the BTUs is not enough. You also have to be aware of how the cool air from indoor air handlers will propagate through your home. A classic question here is if you need a mini split for every room.

You don’t.

A single air handler can adequately cool 2, 3, 4, or even 5 rooms. What you need to remember, however, is that all those rooms are considered an open space – no closed doors between them.

Example: Let’s say you have an 18,000 BTU mini split in the living room. 18,000 BTU can cool down rooms with combined square footage of about 900 sq ft. That means that 1 mini split can cool your living room, adjacent kitchen, adjacent bathroom, and even an adjacent bathroom.

How many rooms can a mini split cool basically depends on your layout. With an open layout and no closed doors, the more powerful air handlers (18,000 BTU and above) can cool 3 or 4 rooms.

how many rooms can mini split cool
Left: A house with small rooms will require several smaller mini splits (below 15,000 BTU). Right: Such a big open space can be cooled using a big 18,000+ BTU unit.

Nonetheless, a better practice is to use smaller (below 18,000 BTU) air handlers and install more of them.

In our example above for a 3,000 sq ft house, the most optimum number of mini splits would be 5 or 6. These include a combination of smaller 9,000 BTU and 12,000 BTU units that can cool 1 or 2 rooms (two rooms have to be adjacent to each other, without closed windows).

Using smaller units will enable multiple points of airflow. With multiple units cooling your house, it’s easier to get a homogeneous temperature through the house. If you would use bigger units, you might run into some hot pockets in rooms the farthest away from the air handler.

using more small mini splits with ensure homogenous temperature throughout the house
To ensure the temperature is the same in the kitchen, living room, bedroom, bathroom, and so on, it is advised to use several smaller mini split air handlers.

To help you make a rough estimate of how many zones mini split you need, we have created this Mini Split Number Calculator. It uses a 20 BTU per sq ft rule of thumb and will tell you how many 12,000 BTU air handlers you need to adequately cool your home:

Mini Split Number Calculator

Just insert the square footage, and you will get the result (we’ll explain how to read this result below the calculator):

As you can see, the calculator tells you exactly (to the 1st decimal point) how many mini splits you need. For a 1,500 sq ft house, you would need 2.5 12,000 BTU mini splits. In these cases, it’s always better to round up the number. Namely, for a 1,500 sq ft you would need 3 12,000 BTY mini splits. You could also use 2 12,000 BTU units and 1 9,000 BTU unit.

You can play around with the numbers to see how the number of mini splits needed changes. You can also consult this chart to see how many mini splits you would usually need to cool certain square footage:

Mini Split Number Chart

Home Size (Square Footage): Number Of Mini Splits Needed:
500 Sq Ft 1 Mini Split
750 Sq Ft 1-2 Mini Splits
1,000 Sq Ft 1-2 Mini Splits
1,250 Sq Ft 1-3 Mini Splits
1,500 Sq Ft 2-3 Mini Splits
1,750 Sq Ft 3-4 Mini Splits
2,000 Sq Ft 3-5 Mini Splits
2,500 Sq Ft 4-5 Mini Splits
3,000 Sq Ft 5-6 Mini Splits
3,500 Sq Ft 5-7 Mini Splits
4,000 Sq Ft 6-8 Mini Splits

This chart gives you a general idea of how many below 15,000 BTU mini splits you would need to adequately cool your home.

Hopefully, you now have a bit clearer understanding of how to pick the right number of mini splits.

Of course, every house is unique and you would need a custom-tailored estimate of how many mini splits you indeed need. If you have a bit of difficulty finding adequate information in this article, you can give a bit of information in the comment section below and we’ll try to help you out.

For specific suggestions on which multi-zone mini splits you can check:

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