Furnace BTU/Sizing Calculator
Find the right furnace size for your home based on square footage, climate, and insulation.
Furnace BTU/Sizing Calculator
Enter your home details below to find the recommended furnace size.
Frequently Asked Questions
What size furnace do I need?
A general rule is 30–60 BTU per square foot depending on your climate. A 2,000 sq ft home in a cold climate needs about 80,000–100,000 BTU, while the same home in a mild climate needs 50,000–60,000 BTU.
What happens if my furnace is too small?
An undersized furnace runs constantly, cannot maintain temperature on the coldest days, and wears out faster due to overuse. Energy bills will be higher despite the smaller unit.
What happens if my furnace is too big?
An oversized furnace short-cycles (turns on and off frequently), leading to uneven temperatures, excess humidity, higher energy bills, and premature wear on components.
How does climate affect furnace size?
Colder climates require more heating capacity. Homes in Minnesota need about 50% more BTU per square foot than homes in Georgia due to longer, colder winters.
Does insulation affect furnace sizing?
Significantly. A well-insulated home may need 25–30% less heating capacity than a poorly insulated home of the same size. Upgrading insulation before replacing your furnace can mean buying a smaller, less expensive unit.
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