Single Zone Mini Split System Sizing Calculator

Sizing Guide Step Two:

Use the calculator to help you figure out what size BTU mini-split system you need for your single zone by selecting the square footage range that best fits your measured zone. You can also select the mini-split type you want to help narrow results to your direct needs. If you are unsure about the mini-split type, see the guide for types below.

Mini Split System Calculator

Please enter your room sizes to narrow your results

Information that can make your head hurt

We provide the easy calculator above to help you narrow down the results. However, we have a formula below to help you confirm that you are selecting the correct sized units if you want to get into the mathematical formula of sizing.

First measure the room or each zone you plan to heat and cool. Once you have the square footage of each zone, multiply the square footage by 25. This new number is the BTU’s needed for that zone. Below is an example of a 3 zone or 3 room system.

Room 1 measures 20 feet x 20 feet
20 feet multiplied by 20 feet gives a total square footage of 400 square feet
400 square feet multiplied by 25 gives us 10,000 BTU’s needed

Room 2 measures 15 feet x 25 feet
15 feet multiplied by 25 feet gives a total square footage of 375 square feet
375 square feet multiplied by 25 gives us 9,375 BTU’s needed

Room 3 measures 30 feet x 20 feet
30 feet multiplied by 20 feet gives a total square footage of 600 square feet
600 square feet multiplied by 25 gives us 15,000 BTU’s needed

With our scenario above the system would need to have indoor units that meet or exceed 10,000 BTU’s for room 1, 9,375 BTUs for room 2, and 15,000 BTU’s for room 3. Since these are very specific sizes we would typically recommend you to go with a 12,000 x 12,000 x 15,000 BTU system or more commonly referred to as a 12 x 12 x 15.

All systems on our site already calculate the outdoor unit size so you do not need to worry about sizing that incorrectly.

Please note that this is a general rule of thumb and different climates will require different sized units. To ensure that you are sizing the unit correctly, it is always best to contact your installer to ensure that the units you are planning on purchasing is what he or she recommends.

Rule of Thumb

A good rule of thumb is to take the square footage from the zone you need to heat/cool, and to multiply by 25. That will give you a good idea of the BTUs that are needed to adequately heat or cool the zone.

Note that this is just a rule of thumb and different factors such as geographical location, climate, windows in zones, and more can change the BTUs needed.

Size Chart:

Square Footage	BTU	Tonnage

Wall Mounted

Most common and popular choice
Easy to install, efficient, most economical
Exterior or interior wall installation
Sleek, modern profile
Mounted about 6ft above floor and 6in below ceiling
Draws air through top vents, releases conditioned air through bottom louvers

Ceiling Cassette

Second most popular air handler type
Discreet appearance like vent cover
Ideal when space is limited or need ot hide unit
Install in drop ceiling or between joists
High-efficiency similar to wall-mounts
Air dispersed in 4 directions from center installation

Concealed Duct

Connected to ducting in installation space
Versatile Installation: above ceiling, below floor, behind soffit
Attach flexible ducting for multi-room heating/cooling
Cost-effective for multiple spaces for one air handler
Fully hidden system with only the air vent covers visible

Floor Mounted

Wall-mounted at/below floor level
Slim profile
Suitable when higher wall installation is not possible
Ideal for A-Frame, attic, and above-garage spaces

Low Wall/Ceiling Mount

Versatile installation:
- Wall-mounted at/below floor level
- Ceiling-mounted horizontally
Ideal for space-saving with limited wall space
Visible body (9-inch drop) compared to ceiling cassette
Economical choice when aesthetics are not priority