Furnace Size Calculator: What Size Furnace Do I Need?

How many BTU furnace would fit your home perfectly?

Most homeowners have difficulties figuring out what size of furnace do they need. Fortunately, calculating furnace size (be it natural gas, propane, or oil) is not rocket science.

To help future furnace owners out, we have developed a simple furnace sizing calculator.

You only need to know two things; your home square footage and the climate zone you’re in. 

After the furnace sizing calculation, you’ll find how the size of the furnace is calculated. We also made 3 examples for:

  1. What size furnace do I need for a 1000 sq ft house? (Example 1)
  2. What size furnace do I need for a 2000 square foot home? (Example 2)
  3. What size furnace do I need for a 3000 sq ft home? (Example 3)

For an exact estimation of furnace size, you should ask your local furnace installers. You can 

Furnace BTU Calculator (Input Square Footage And Climate Zone)

0.00 BTU

Furnace Capacity

 

You can freely use the calculator to roughly estimate the capacity of a furnace you need.

The basic principles the furnace sizing calculator is based on are:

  • Larger homes need more BTU than smaller homes (directly proportional to square footage).
  • Homes in colder climates (Region 5; Example ) need to generate more heat than holmes in warmer climates (Region 1; Example

In order to properly size a furnace, we need to use BTU heating needed per square foot for each climate zone:

Region 1 Region 2 Region 3 Region 4 Region 5
35 BTU per sq ft 40 BTU per sq ft 45 BTU per sq ft 50 BTU per sq ft 60 BTU per sq ft

Essentially, homes in the far North (Minessota, for example) need almost twice as much heating as homes in the far South (Texas, for example).

Here are the 3 examples that illustrate how the calculator works.

What Size Furnace Do I Need For A 1000 Sq Ft House? (Example 1)

Let’s say we have a nice 1,000 square foot home in Los Angeles, California. We need two data points:

  1. Home square footage: 1,000 sq ft.
  2. Climate zone: Los Angeles, California, is in Region 2.

We input both of these data points in the calculator. Here is what we get:

for 1000 sq ft home we need 40000 btu furnace

In short, we need a 40,000 BTU furnace.

What about if we have a 1,000 sq ft home in the heart of Minnesota? That’s Region 5. Here is what we get with the furnace sizing calculator:

in cold climate 1000 sq ft home needs 60000 btu furnace

We see that for a 1,000 sq ft home we need:

  • 40,000 BTU furnace in California.
  • 60,000 BTU furnace in Minnesota.

Here are the results for 1000 square foot houses in all climate zones:

Region 1 Region 2 Region 3 Region 4 Region 5
35,000 BTU 40,000 BTU 45,000 BTU 50,000 BTU 60,000 BTU

What Size Furnace Do I Need For A 2000 Square Foot Home? (Example 2)

2000 sq ft houses need double the furnace capacity compared to 1000 sq ft house.

Here are calculated 2000 sq ft home estimates for furnace size:

Region 1 Region 2 Region 3 Region 4 Region 5
70,000 BTU 80,000 BTU 90,000 BTU 100,000 BTU 120,000 BTU

What Size Furnace Do I Need For A 3000 Square Foot Home? (Example 3)

Furnace size for a 3,000 square foot home range from 105,000 BTU to 180,000 BTU, depending on the climate zone you’re in. Here is a table with calculated 3,000 sq ft furnace sizes for all 5 regions:

Region 1 Region 2 Region 3 Region 4 Region 5
105,000 BTU 120,000 BTU 135,000 BTU 150,000 BTU 180,000 BTU

We hope everybody will be able to use the furnace capacity calculator and get a good estimate of the size of the furnace they need for the winter heating

You can check our articles about different types of heating furnaces:

1 thought on “Furnace Size Calculator: What Size Furnace Do I Need?”

  1. Many factors other than building square footage need to be considered before choosing a furnace but it gives you a ballpark estimate to start with.
    The size and type of duct work also needs considered.
    The ceiling height and the amount and type of insulation in the attic and walls.
    A 3000 sqft home with 11 foot ceilings will need a much larger furnace than one with 8ft ceilings.
    And those with 20ft high cathedral ceilings and “open” concepts may result in all the money you spend for heat merely keeping the ceiling warm instead of you.
    The type of windows and doors also need to be factored in.
    Are you on a hill top or in a valley or in town where winds are buffered and blocked.
    What is the coldest temperature you have had in the past.
    HVAC companies often tell homeowners their old furnace was oversized and recommend a much smaller furnace.
    Then when those nights hit 25 below, their new furnace is running constantly and can’t keep up.
    It really takes a professional with decades of experience to make these determinations so it’s not a DIY project.

    Reply

Leave a comment