How Many Square Feet Does a 3 Ton Air Conditioner Cool
Tips & Tricks

How Many Square Feet Does a 3-Ton Air Conditioner Cool?

When shopping for an air conditioner, choosing the appropriate size is important to get the most out of it. The smallest residential AC capacity is 1.5 tons(18,000 BTUs), while the largest is 5 tons(60,000 BTUs).

The 3-ton air conditioning units are the most common sizes in residential homes. So if you’re considering buying a 3-ton air conditioning unit, we are sure you’re wondering if it’s the right size for your space.

Generally, a 3-ton AC unit will comfortably cool a 1,800 square foot room if it’s well-insulated. But other factors may require getting a smaller or bigger AC unit. Incorrectly sizing an AC unit can cause thousands of wasted AC and electricity costs.

So to ensure you make the right decision, we will discuss how to properly size an AC system and the correct space size for a 3-ton unit.

What is air conditioning tonnage?

Air conditioning tonnage is the term used for rating air conditioning units. It has nothing to do with weight. Instead, an HVAC ton describes how much heat an AC unit can remove from the space within one hour.

The SI unit measuring heating and cooling performance is the British Thermal Unit(BTU). Therefore, a 1-ton unit equals 12,000 BTUs.

The tonnage of an AC unit is important as it determines the size of the AC unit that will adequately cool your home or room. The more tonnage an AC unit has, the more air it can cool. Some people think the bigger the AC unit, the better; however, that’s false.

A large AC unit for your room will cool the space too quickly. As a result, the compressor will cycle continuously, thus reducing its energy efficiency and increasing costs.

On the contrary, an AC unit that is too small for your home will constantly run to cool the space, and sometimes it may never achieve the desired temperature. This will increase your energy costs and put additional strain, leading to the AC’s premature failure.

How many square feet will my 3-ton air conditioner cool?

The standard practice among HVAC experts is to use 1 ton of AC capacity for every 600 square feet of space. So a 3-ton air conditioner can cool about 1,800 square feet of room with a typical 8-foot ceiling, relatively good insulation, and newer-style windows.

Three tons equals 36,000 BTUs; you need about 20 BTUs per square foot. So, 36,000 ÷ 20 = 1,800 square feet for a 3-ton AC. However, the exact figure could be slightly lower or higher, depending on climate, ceiling height, insulation quality, number of occupants, presence of heat-producing appliances, and many more factors.

Air conditioning sizing chart by total square footage

There are three ways to find the correct AC unit for your square feet. They include; using an industry chart, online calculators, and manual calculations.

However, the easiest way is to use an air conditioner and a home size chart. It allows you to conveniently match the exact AC size based on the total square footage of your space in a moderate climate.

Square footageBTUTons
600 – 1000180001.5
1000 – 1300240002
1300 – 1600300002.5
1600 – 1900360003
1900 – 2200420003.5
2200 – 2600480004
2600 – 3200540004.5
3200 – 3300600005

Factors that determine AC size

Several factors affect the air conditioner size suitable for your room. Here are the main ones:

  • The number of rooms: The number of rooms you intend to cool will determine the size of your unit. The more the rooms, the more cooling power your need to ensure optimal comfort and efficiency.
  • Size of each room: Generally, you need 20 BTUs for every square foot. So, a 600-square foot room will require a bigger unit than a 100-square foot room.
  • Appliances: If you have heat-generating appliances like cookers, ovens, and TVs, you will need an AC unit with more cooling power to achieve the desired temperature. So, a small kitchen may require a bigger AC compared to a larger room with no heat-generating appliances.
  • Ceiling height: Any additional foot between the floor and ceiling means more air volume to cool. So any room with a higher ceiling will require a bigger AC unit.
  • Climate: The geographical location and weather influence the amount of cooling needed to keep your home comfortable. The hotter the location, the more cooling power is needed. Here is a guide from the U.S Department of Energy to help homeowners determine their climate zone.
  • Occupancy: The average AC size a manufacturer suggest is for single occupancy. So you need about 600 BTUs for every additional occupant because of more body heat in the space.
  • Insulation: The quality of your home’s insulation will affect the size of your AC unit. A home with great insulation will hold cold air more effectively, be easier and less expensive to cool, and require less tonnage. So if your space has old ductwork, air can escape, thus requiring more cooling power.
  • Exposure to sunlight: Also, sunlight will heat your home very quickly. So if the room you’re cooling receives more sunlight and your windows have no proper sunblocks, you will need a more powerful AC to keep the space cool.
  • Windows and doors: Windows and doors can be a source of energy loss in the room, especially if they are single-paned. Single-pane windows are less energy-efficient than double-pane, triple-pane, or low-emissivity film-coated windows. So energy-efficient windows can reduce the AC tonnage required.

What is the price difference between 2.5 and 3-ton AC?

In the price difference between a 2.5-ton AC unit and VS 3-ton, the 2.5-ton unit will be considerably cheaper than the 3-ton one. The general cost of a 2.5-ton AC is about $2800-$2900, while a 3-ton unit is about $2900-$3300.

The difference may not be as significant, but their running costs will vary. This is because the higher the cooling capacity of an AC unit, the more energy it uses to cool your space.

So if you want an energy-efficient air conditioner, look at their SEER rating. The ideal scenario is having a unit with a high SEER rating and a low cooling capacity. Unfortunately, there is no standard SEER value according to tonnage.

But a 3-ton AC (36,000 BTUs) with a higher SEER rating (such as 17) will have a considerably lower electricity cost compared to a 2.5-ton unit with no SEER certification.

Once you know the BTU requirements, you can make a good decision. Once you get the appropriate AC size, you should learn how to make your AC cool better to reduce running costs.


We have learned that air conditioner size depends on the size of your home and other factors affecting energy loss or production in that space. Ideally, a 3-ton AC unit will cool about 1,800 square feet of living space.

However, that value may vary depending on other factors such as geographical location, number of occupants, insulation, ceiling height, and others. Since air conditioner tonnage isn’t so straightforward, we recommend hiring an HVAC to visit your space and help you size your air conditioning system.