AC Tonnage Calculator: What Tonnage AC Do I Need?

mother and child adjusting temperature in home
Photo: Halfpoint / Adobe Stock
mother and child adjusting temperature in home
Photo: Halfpoint / Adobe Stock
Stephanie Mickelson
Written by Stephanie Mickelson
Contributing Writer
Updated May 29, 2025
Highlights

  • Calculating tonnage for your AC can help the system run efficiently.

  • Square footage is the primary factor when calculating AC tonnage.

  • Sunlight, ductwork and insulation, heat-generating appliances, and climate affect tonnage.

  • Installing a new AC unit costs between $3,906 and $8,020.

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Air conditioner tonnage is a measure of how large an air conditioner is and, therefore, how much cooling capacity it has. Tonnage refers to how many BTUs of heat the AC can remove each hour—one ton of cooling equals 12,000 BTUs of heat removed per hour. If you’re wondering, “What tonnage AC do I need?” we can help. Calculating tonnage will help you choose the unit that has a sufficient cooling capacity without being too large or too small.

What Tonnage AC Do I Need?

ac outside brick home
Photo: Chad Robertson / Adobe Stock
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When it’s time to upgrade your AC, you can get a good idea of the AC tonnage you need by estimating based on the size of your home. You’ll also need to consider other factors like insulation, type of AC unit, amount of sun exposure, usage of heat-generating appliances, the region you live in, and home features that can modify the temperature, like a fireplace, among others.

Using the square footage of your house, refer to the chart below to get an estimate of AC tonnage.

Square FeetAC Size
6001–2 tons
1,0002 tons
1,5003–4 tons
2,0004 tons
2,5005–6 tons
3,0006–7 tons
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Calculating AC Tonnage

To calculate AC tonnage, you’ll need to know how many square feet your home is and then apply the following formula:

AC Tonnage = (Square feet x 25) / 12,000

How to Calculate Square Feet

Before you can determine the AC tonnage you need and choose a central air conditioner, you should measure the square footage of your home. To do this, measure the length and width of each room and multiply them together. You may have to break the room into smaller sections or regular shapes for large or irregularly shaped rooms. 

Once you have the measurements of each room, add them together to determine the total square footage.

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Who to Hire to Calculate AC Tonnage

A local HVAC pro can come to your home and estimate the tonnage of your new AC unit. Using the square footage as a starting point, they’ll also take other factors into consideration, including the quality and condition of your ductwork and insulation, the amount of direct sun exposure your home gets, the quality of the number of windows and doors, the material your home is made of, and the local climate. Using all of these inputs, they’ll be able to give you an accurate estimate so you can purchase the right size air conditioning unit.

Frequently Asked Questions

A one-stage air conditioner only has one setting, while a two-stage air conditioner has a high and low setting. A two-stage air conditioner costs between $500 and $2,500 more than a traditional air conditioner, but it has a longer lifespan and helps to increase energy efficiency. To make this decision, you should consider your energy needs and available budget.

Replacing an AC unit costs between $3,906 and $8,020 and the average cost falls at $5,958. Factors that affect the final cost include the type of air conditioner, its size, the region you live in, the unit’s efficiency, and installation costs. In some cases, if the unit is less than 10 years old and it will cost less to repair rather than replace, it makes more sense to repair the AC unit rather than replace it.

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Learn more about our contributor
Stephanie Mickelson
Written by Stephanie Mickelson
Contributing Writer
Stephanie Mickelson is a freelance writer covering home improvement, real estate, design, and personal finance. Before beginning her freelance career, she worked in residential construction, specifically remodeling kitchens, installing cabinets, flooring, countertops, trim, and more.

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