Furnace Sizing Calculator
Estimate furnace BTU size for any home.
Furnace size in BTU is roughly the heated square footage × the climate factor: 30–35 BTU/sq ft in mild zones, 40–45 in moderate zones, 50–60 in cold zones. A 2,000 sq ft home in a moderate climate needs about 80,000–90,000 BTU input. Divide by the AFUE rating for output. Enter your home details for a sized furnace.
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.
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