Furnace Sizing Calculator — BTU by Home Size

How the furnace sizing calculator works

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).

Frequently asked questions

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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