Furnace Sizing Calculator
Estimate furnace BTU size for any home.
A furnace sizing calculator estimates the required furnace output by multiplying your home’s area in square feet by a climate factor in BTU/ft². Typical climate factors range from 30 to 60 BTU/ft². Round the result up to the nearest standard furnace size: 60, 80, or 100 kBTU.
Furnace output
60,000
BTU/hr
Rounded size
60
thousand BTU/hr
Zone guide
Mild
30–60 BTU/ft²
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How does the furnace sizing calculator work?
Furnace output = home area (ft²) × climate factor (BTU/ft²). Typical factors: hot climate 30, mild 40, cold 50, very cold 60. Then round up to the nearest standard size (60, 80, 100 kBTU).
What else do people ask about this calculator?
What size furnace for a 2000 sq ft house?
In a mild climate (~40 BTU/ft²), about 80,000 BTU/hr. In a cold climate (~50), plan on 100,000 BTU/hr.
Is a bigger furnace better?
No — oversized furnaces short-cycle, wear faster, and leave humidity high. Right-size to your load.
Which related calculators should I use next?
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