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

You’ve decided that it’s time to add more cooling to your home, perhaps to supplement the old central air system or replace it altogether. Or maybe you recently added an addition to your home and now require a new air conditioning system to serve the new area.

Unfortunately, you’re not sure about the sizes. You believe you need somewhere in the region of 3.0 tons. However, you’re not completely sure whether that would be enough or even if it may be too much.

This guide is specifically designed with shoppers like you in mind. We explain how to properly size your mini-split system, the dangers of an under or oversized ac, and, ultimately, the correct applications for a 3-ton unit.

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

The average space that you can comfortably cool with a 3-ton air conditioner is 1,800 square feet. The math is easy. Three tons equals 36,000 BTUs, and you need about 20 BTUs per square foot. 36,000 ÷ 20 = 1,800. However, remember that the actual figure can be much higher or lower, depending on several factors.

Understanding Air Conditioner Sizes 

The first thing you need to understand is how air conditioner sizing works, and what better place to begin than understand the British Thermal Unit metric and the values behind it?

What is BTU?

Heating and cooling performance are measured in British Thermal Units (BTUs). A British Thermal Unit measures the heat content of fuels or energy sources.

For example, one BTU is the quantity of heat required to raise (or lower) the temperature of one pound of liquid water by 1°F at the temperature that the water has its greatest density (approximately 39°F).

In the context of air conditioning appliances, an appliance’s BTU rating/value denotes the amount of heat it can remove from a typical indoor space per hour.

Therefore, a 30,000 BTU air conditioner can remove 30,000 BTU of heat from a space per hour, while a 10,000 BTU air conditioner removes 10,000 BTU of heat per hour.

What’s an AC Ton?

The origin of the term “ton” in the heating and cooling industry is fascinating. Before Willis Carrier invented the modern-day air-conditioning systems in 1902, people cooled buildings in the summer with ice harvested in the winter.

The delivery companies measured the amount of cooling ice in “tons of ice.” Unsurprisingly, this term has stuck to date.

One ton of cooling is the amount of heat needed to melt 2,000 pounds of ice in 24 hours. Thus, a 1-ton unit = 12,000 BTUs = 3.517 Kilowatts = 4.713 Horsepower.  

Factors Influencing AC Sizing 

Several factors affect air conditioner sizing, from the size of your room to the type of air conditioner. However, the seven main factors are;

  • The number of rooms: How many rooms do you intend to cool? One, two, perhaps three? The higher the number of rooms, the more cooling power you need to ensure optimal comfort throughout the house.
  • Size of (each) room: Also important is the size of each room. You may have three rooms to cool, each measuring 100 square feet or just one room measuring 600 square feet. This means you need a bigger air conditioner for the single room. Generally, you need 20 BTUs for every square foot.
  • Appliances: Heat-generating appliances, such as TVs, electric and gas cookers, and other electronics typically require more cooling power to maintain the thermostat setting. So, for example, you need a bigger air conditioner even in a relatively small kitchen.
  • Ceiling height: Every additional foot between the floor and the ceiling means more air volume to cool. For instance, assuming a uniform floor size of 10 x 10 feet, an empty room with a 7-foot ceiling has 700 cubic feet of air while one with a 9-foot ceiling has 900 cubic feet of air. So, you need more cooling power for the 9-foot ceiling room.
  • Climate: The prevailing weather directly influences the amount of air conditioning needed to keep your home cool and comfortable. Thus, the location’s weather is critical to air conditioner sizing. The hotter the location, the greater the cooling needs.
  • Occupancy and number: Is the home/room occupied? If so, by how many people? The average figures you keep seeing on the internet are for single occupancy. You need an additional 600 BTUs for every additional occupant.  
  • Insulation: Finally, the correct AC size also depends on your room or home’s insulation quality. You may need up to 20% more air conditioning for a poorly insulated home.  

The Importance of a Size AC 

Maybe you’re wondering whether you can under or over-size your air conditioner without adverse consequences. Unfortunately, you can’t.

Dangers of Under-size AC

Selecting an air conditioner too small for your needs is asking for trouble. The following are some of the potential consequences.

  • Overworking: The air conditioner may run continuously because it must work harder to keep up with the cooling demands.
  • Faster wear and more repairs: Overworking the air conditioner often leads to faster wear and tear, thus a shorter appliance life. You’ll also need frequent repairs.

Dangers of AC Over-Sizing 

Oversizing is also not recommended as it can damage your air conditioner. Some of the dangers of over-sizing an air conditioner include;

  • Short-cycling: You may notice that your air conditioner starts and stops frequently. This is known as short cycling. Short cycling is bad for the health of the AC and may also interfere with humidity levels.
  • Unnecessarily high energy bills: Remember that a bigger air conditioner draws more electrical power. Start-up power is especially high in larger ACs. This can result in unnecessarily high energy bills.

Three Ways to Size an AC 

There are three broad ways to determine the correct air conditioner size (in BTUs) for any specific application;

Use Industry Averages

The following are the industry averages that everyone uses for general guidance on proper air conditioner sizing (the room sizes are square feet).

  • 550 sq. ft. = 1.0 tons AC
  • 700 sq. ft. = 1.5 tons AC
  • 1,000 sq. ft. = 2.0 tons AC
  • 1,400 sq. ft. = 2.5 tons AC
  • 1,800 sq. ft. = 3.0-ton unit
  • 2,000 sq. ft. = 3.5-ton AC
  • 2,500 sq. ft. = 4.0-ton unit
  • 3,000 sq. ft. = 4.5-ton unit

*Based on the average home in a moderate climate

Use Online Calculators

Alternatively, you can use online calculators to determine your application’s correct air conditioner size. The main advantage of using BTU sizing calculators is that they consider all the important factors and allow you to specify your unique needs.

For instance, you can specify your home’s insulation level, geographic location, and the number of occupants. You can also specify your property’s exposure to sunlight.

The best part is that you don’t need special skills or know-how to use an air conditioner sizing calculator.  

Calculate Manually 

Finally, you can calculate your air conditioning needs manually. This can be a little confusing if it’s your first time sizing an air conditioner unit.

However, it works like a charm and is the most accurate way to calculate your BTU requirements if you have some experience or know-how.

Begin with the assumption that you need about 20 BTUs per square foot for a home with an 8-foot ceiling.

Then adjust accordingly based on the size of the home/room, your geographic location, the home’s insulation level, and the other factors discussed earlier.

How Many Square Feet Does a 3-Ton AC Cool? 

Generally, a 3.0-ton air conditioner can comfortably cool a 1,800-square-foot space. However, the exact figure can be slightly higher or lower, depending on your geographic location, the space’s insulation quality, exposure to sunlight, and many other factors.

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

What Size House will a 2-ton AC Unit Cool? 

A 2-ton air conditioner is ideal for a 1,000 square-foot home or space. Meanwhile, a 2.5 tons AC unit will comfortably serve a 1,400 square-foot home or area.

Is a 3-Ton Air Conditioner Enough? 

It depends on your cooling needs. The rule of thumb is to never exceed or under-size your air conditioning requirements by more than 15%. This means that you cannot install a 3-ton (36,000 BTU) air conditioner in applications requiring less than 30,600 BTU or those requiring more than 41,500 BTUs.

What size AC do I Need for 2,000 Square Feet? 

You need a 3.0 ton (36,000 BTUs) to 3.5 ton (42,000 BTUs) AC for a 2,000 square-foot home. It comes down to other factors, such as your geographic location and the number of occupants. 

How Many Tons do you need for a 1,400 sq. ft. House? 

Generally, you need a 2-ton air conditioning unit for a 1,000 square-foot house. However, you may need slightly more cooling power if the house has more than one occupant and is directly exposed to sunlight, among other factors.

What SEER AC should I get? 

A value between 15 SEER and 18 SEER is ideal for most homeowners because appliances in this range offer excellent efficiency levels without burning a hole in your pocket.


BTU sizing isn’t as straightforward as many people think. Although you can use industry averages for base calculations, it’s always better to factor in important considerations, such as your geographic location and the number of people living in the house, for more accurate sizing.

That said, though, a 3-ton air conditioning unit is good enough for a 1,800 square-foot area.