HVAC Size Calculator: What Size HVAC Unit Do I Need?

You will need a 1.5 ton to 5.0 ton unit, either an AC for cooling along with a furnace or a heat pump that will both heat and cool. If your split system includes central air and a gas furnace, the furnace size will range from 45,000 to 135,000 BTU.

Choosing the proper size equipment, a process known as “sizing” your HVAC system, is essential to indoor comfort including temperature balance and humidity control throughout the year.

Note: 1.5 to 5.0 tons for AC or a heat pump is equivalent to 18,000 to 60,000 BTU.

Note: 1.5 to 5.0 tons for AC or a heat pump is equivalent to 18,000 to 60,000 BTU.

The right size HVAC unit or system is selected by a qualified pro based on your climate zone, homes’ square footage, insulation condition, and how sunny it is where you live.

This page will give you an accurate estimate to the question – What size HVAC unit do I need?

It includes an HVAC Size Calculator that is the most accurate of its kind.

HVAC Size Calculator

Using the estimator is quite simple. There are a few common questions immediately below the estimator, and then we’ll provide a few tips and suggestions below the calculator as each input box is explained.

HVAC Size Calculator

Locate your climate zone on the map above and provide your square footage. You'll get how many BTUs needed for your HVAC.

See the climate zone map above to find your home's climate zone

What size HVAC for 1500 sq ft?

The HVAC size is 2.5 to 3 tons for the AC and 70,000 BTU for the furnace. That’s in Zone 4 – a zone with average temperatures. However, to get exact HVAC sizing for your home, fill out all the details in the calculator.

What size hvac for 1800 sq ft?

According to the calculator, a 2.5 to 3 ton AC will do the job along with an 80,000 BTU furnace. But again, it depends on all the factors considered in the calculator.

Four Steps to Understanding the HVAC Size Calculator

Step 1: Climate Zone

Looking on the map, locate the zone where you live. If you happen to be close to two different zones, you should use the zone that is the higher number, which is the cooler zone.

Why? Because you might end up with an AC that is slightly too large, and that’s not a big deal. But it would be a big deal if the furnace were too small, so going up a Zone if you’re close to the edge will guarantee you get enough furnace to keep your home comfortable.

Step 2: Home Size

Fill in the square footage of your home, if you happen to know it.

If you don’t know the square footage, you can possibly find the square footage number on your home’s blueprints that would be located on closing documents. If that number is still unavailable, you can figure out the square footage yourself by using the area formula (length x width).

Simply determine the area of each room in your home and total the room sizes up to get the total square footage in your home.

What about the basement? If you intend to heat it, include it in your square foot total.

Step 3: Insulation Condition

You have three options to decide from when determining the insulation condition of your home. Choose the one that works best for your house.

Good Condition: To determine that your home’s insulation is in “good” condition you will need the following: a house wrap (Tyvek), ample insulation in your attic, and energy efficient windows and doors.

Average Condition: If your home was built between 1990 and 2010 and has not been updated to make it “energy efficient,” you would consider the insulation of your home to be in “average” condition. Some homes that were built pre-1990 with upgraded windows, doors, and/or insulation can also be considered to be in “average” insulation condition.

Poor Condition: Older homes that have not been updated would be considered to have “poor” insulation conditions. The windows and doors are not sealed well and some rooms are either cooler or hotter than others, depending on the season. Homes in “poor” condition tend to be drafty.

Step 4: Sun Exposure

How sunny is it where you live? This is a general question – or if you want to get specific, you can find the number of sunshine hours that is average for your state.

If the number is above 3,000, like Arizona and Colorado, you live in a sunny spot. Between 2,400 and 3,000, like North Carolina and Maryland, is considered average. Below 2,400 like Oregon and Michigan would be called a cloudy area.

Results: The Recommended HVAC Unit Size

Once everything is filled in on the calculator, it will crunch the numbers and give you the results – the size of both the air conditioner or heat pump and furnace BTUs if included in your HVAC system. .

Check Your Results: Sample HVAC Sizing Tables

For the examples below, the zones are noted, the insulation condition is considered “average,” and the sun exposure is “very sunny” for the hot climate, “sunny” for the warm climate, and “heavily shaded” for the cold climate.

We’re considering that the system will include central air conditioning and a furnace.

What size HVAC unit do I need for a 1500 square foot home with average insulation condition?

What size hvac for 1500 sq ft?

Hot Climate (Zone 2)

Warm Climate (Zone 4)

Cold Climate (Zone 6)

AC Size

2.5 - 3.5 Ton

2.5 - 3 Ton

2 - 2.5 Ton

Furnace Size

41,000 - 48,000 BTU

60,000 - 70,000 BTU

91,000 BTU

What size HVAC unit do I need for an 1800 square foot home with average insulation condition?

What size hvac for 1800 sq ft?

Hot Climate (Zone 2)

Warm Climate (Zone 4)

Cold Climate (Zone 6)

AC Size

3 - 4 Ton

2.5 - 3.5 Ton

2.5 - 3 Ton

Furnace Size

49,000 - 57,000 BTU

80,000 - 90,000 BTU

100,000 - 110,000 BTU

What size HVAC do I need for a 2200 square foot home that has average insulation condition?

Hot Climate (Zone 2)

Warm Climate (Zone 4)

Cold Climate (Zone 6)

AC Size

4 - 5 Ton

3.5 - 4 Ton

2.5 – 3.5 Ton

Furnace Size

66,000 – 77,000 BTU

90,000 - 99,000 BTU

120,000 – 130,000 BTU

HVAC Size Chart

The HVAC sizing estimator above is a great way to determine the HVAC size that you may need to keep your home more comfortable. Another useful tool is the HVAC size table below.

You can simply locate the size of your home, and find out what size of AC or Heat Pump you will need, as well as the estimated furnace size that your home will also require. Please keep in mind that all the information in the HVAC size table is based on a moderate climate zone with average insulation and sun exposure.

HVAC Size For Square Footage

house sizeAC or Heat Pump SizeFurnace Size
1,000 sq ft1.5 - 2 Ton45,000 Btu
1,200 sq ft2 Ton54,000 Btu
1,300 sq ft2 - 2.5 Ton59,000 Btu
1,400 sq ft2 - 2.5 Ton63,000 Btu
1,500 sq ft2.5 - 3 Ton68,000 Btu
1,600 sq ft2.5 - 3 Ton72,000 Btu
1,700 sq ft2.5 - 3 Ton77,000 Btu
1,800 sq ft2.5 - 3.5 Ton81,000 Btu
1,900 sq ft3 - 3.5 Ton86,000 Btu
2,000 sq ft3 - 3.5 Ton90,000 Btu
2,100 sq ft3 - 4 Ton95,000 Btu
2,500 sq ft4 - 4.5 Ton113,000 Btu
3,000 sq ft4.5 - 5 Ton135,000 Btu

* Based on moderate zone 

Frequently Asked Questions

How much does it cost to install a central air conditioning unit?

It will cost, on average, between $6,000 and $7,000 to install a central air conditioning system in a 1,500 square foot home. A large, 3,000 square foot home, will cost up to $10,000. These prices include the AC or Heat Pump and the installation costs.

Why are air conditioners rated by using “tons”?

A ton, in the HVAC world, refers to the amount of heat that is removed by the AC or Heat Pump in one hour. The amount of heat is then measured in British Thermal Units (BTU). A ton is determined by the amount of heat that is required to melt one ton of ice. One ton is equivalent to 12,000 BTUs.

What are some of the most popular HVAC systems?

A standard split system using an AC and furnace remains the most common. Heat pump systems with a heat pump and air handler are growing in popularity. They come in standard split systems and mini split systems with one outdoor unit and up to 8 indoor units depending on system size. In a mini split system, each indoor unit is installed in the room or zone it will serve. There is no ductwork – these are also called ductless systems for this reason.

Boilers with baseboard heaters, aka radiators, or radiant floor heat, also called hydronic heat, are preferred in some homes where an air handler blowing dust around isn’t appreciated because of allergies.

How long does an HVAC system last (life expectancy)?

The average life expectancy for an HVAC system is between 15 and 25 years, but you can possibly extend longevity by 5 years or more by having the system maintained on a regular schedule and making minor repairs as needed. by using regular checkups and repairs. A good idea is to have your AC or Heat Pump inspected and maintained regularly by a professional HVAC technician in order to have your

How much does it cost to use your HVAC system?

The average cost, per month, to run your AC system is between $75 and $160 a month, depending on what climate zone you are in.

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