Furnace Sizing Calculator
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What size furnace do I need?
This calculator estimates the heating BTU your home needs from its square footage and climate zone, then converts it to a furnace input size at typical efficiency. Confirm with a Manual J before buying.
Frequently asked questions
How many BTU furnace do I need for 1,500 square feet?
It depends heavily on climate: a mild-climate home needs far less heating BTU than a cold-climate one of the same size. The calculator adjusts for your state’s climate zone.
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