What Size Air Conditioner Do You Need?

KEY TAKEAWAYS

Multiply your square footage by 20, then divide by 12,000 to find the correct AC tonnage
Oversized AC units cool too fast, causing short cycling, uneven temperatures, and more wear and tear, while an undersized one runs constantly and drives up your energy bill
In addition to square footage, ceiling height, insulation quality, window efficiency, sun exposure, and number of occupants should be considered when finding the correct AC size
Not sure what AC size is right? Get a professional load calculation from an HVAC technician

What size air conditioner do I need?

The general rule of thumb for finding the right size air conditioner is to multiply the square footage of your home by 20 BTUs (British Thermal Units).

Next, you can divide the result by 12,000 to find the tonnage because 12,000 BTUs is equal to a 1 ton AC unit.

Use our handy air conditioner sizing chart or custom air conditioner size calculator to match up your home’s square footage to the correct size cooling system.

Square Footage	BTUs Needed	AC Size in Tons
600 square feet	12,000 BTUs	1 ton
900 square feet	18,000 BTUs	1.5 tons
1,200 square feet	24,000 BTUs	2 tons
1,500 square feet	30,000 BTUs	2.5 tons
1,800 square feet	36,000 BTUs	3 tons
2,100 square feet	42,000 BTUs	3.5 tons
2,400 square feet	48,000 BTUs	4 tons
2,700 square feet	54,000 BTUs	4.5 tons
3,000 square feet	60,000 BTUs	5 tons

Air conditioning units come in various sizes, typically measured in BTUs (British Thermal Units) or tons. Common residential sizes range from 1.5 tons (18,000 BTUs) to 5 tons (60,000 BTUs). The air conditioner size your central AC system requires will depend on the total square footage of your living space and each individual room size within it.

When shopping for an AC unit, it’s crucial to match each unit's capacity to the size of the space it will be cooling. An undersized unit will struggle to cool your home, leading to constant running, reduced cooling power, and higher energy costs. However, contrary to popular belief, a larger system doesn’t necessarily optimize performance. Rather, oversized units can cool too quickly, resulting in short cycling, uneven cooling, and increased wear and tear.

Here are some general tips for selecting the right size AC unit:

Know your space: Measure the square footage of the area you want to cool. This is the starting point for determining appropriate air conditioner sizing.
Understand the required BTUs: The higher the BTU rating, the larger the area the system can cool. As a general rule, all manufacturers encode air conditioner size into the model number.
Check the energy efficiency rating: Look for units with a high SEER (Seasonal Energy Efficiency Ratio) rating to ensure maximum efficiency per square foot.
Consult an expert: Hire a professional HVAC technician to perform a detailed residential load calculation, advise you on system capacity, and recommend the air conditioner size.

How to calculate air conditioner size for a house

Having established that choosing the right size air conditioner is essential for maintaining comfort and efficiency, let’s examine a quick reference air conditioner size chart, review some specific examples for common home sizes, and outline a simple formula for custom calculations for properties with an alternative square footage range.

A simple formula for sizing air conditioners

If your home doesn’t fit neatly into the air conditioner unit size guide above, or you’re unsure about which AC unit size would be best, use the following process and formula:

Measure the length and width of each room you want to cool, then simply multiply the length by the width to calculate the square footage.
Add your calculations for each room together to get the total square footage.
Use the formula Total Square Footage x 20 to determine the required BTUs.
Divide by 12,000 to find tons.

For example, if your home is 1,200 square feet:

1,200 x 20 = 24,000 BTUs
24,000 BTUs / 12,000 = 2 tons

What size air conditioner for 500 square feet?

A 500 square foot home would require either a 0.5 or 1 ton AC unit. If you live in a region that does not experience extreme heat, a 0.5 ton unit may be appropriate. In a hot state like Texas, you may be better off with a larger unit to accommodate the weather.

500 square feet x 20 = 10,000 BTUs
10,000 BTUs / 12,000 = 0.83 tons
Speak with a professional to determine whether 0.5 or 1 ton is more appropriate.

What size air conditioner for 1000 square feet?

A 1,000-square-foot area typically corresponds to a modest two-bedroom apartment or a cozy two-bedroom house with a kitchen, dining area, one or two bathrooms, and a living room. Using the AC size formula, a 1,000 square foot would require either a 1.5 or 2 ton AC unit.

1,000 square feet x 20 = 20,000 BTUs
20,000 BTUs / 12,000 = 1.6 tons
Speak with a professional to determine whether 1.5 or 2 tons is more appropriate.

What size air conditioner for 2000 square feet?

For a 2,000-square-foot home, you're likely looking at a spacious three-bedroom house with a kitchen, dining area, two or more bathrooms, a living room, and possibly a separate family room or office space. This size home would require either a 3 or 3.5 ton AC unit.

2,000 square feet x 20 = 40,000 BTUs
40,000 BTUs / 12,000 = 3.3 tons
Speak with a professional to determine whether 3 or 3.5 tons makes sense for your home

What size air conditioner for 3000 square feet?

A 3,000 square foot home would likely be a house with a second floor comprising around four bedrooms, a kitchen, dining area, multiple bathrooms, spacious living room, family room, and potentially additional rooms like a study or home gym. A home this size may require an AC unit between 4-5 tons depending on your regional climate.

3,000 square feet x 20 = 60,000 BTUs
60,000 BTUs / 12,000 = 5 tons

What factors affect air conditioner size?

Aside from the basics of room size and total square footage, there are several additional factors that can influence the size of the air conditioner you need:

Ceiling height: Homes with higher ceilings have greater air space to cool and require more BTUs. Standard calculations usually assume an eight-foot ceiling.
Your home's insulation: Houses with additional insulation retain cool air better, while poorly insulated homes require more BTUs.
Windows: Newer-style windows are better at keeping cool air in, whereas older-style windows are less energy-efficient and may require a more powerful unit.
Sun exposure: Rooms on the south or west sides of buildings that receive more sunlight typically require more cooling power.
Number of occupants: People generate heat. So, the more people that regularly occupy a property, the more BTUs you’ll need.
Appliances and electronics: All electronic devices generate additional heat, which can significantly affect how much energy you use. Using appliances and electronics with an ENERGY STAR label should help with this.
Outdoor vs. window units: An outdoor unit setup will typically have a higher cooling capacity than window air conditioners.

Written by Graham Lumley

Graham Lumley, Growth Product Manager at BKV Energy, leads digital and traditional marketing strategies, focusing on educating Texans about the state's deregulated energy market. With over 10 years of marketing experience, he creates content to help consumers understand and save on their energy bills, bringing a fresh and dynamic approach to the industry.