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Easily find the right furnace size for your home with our free online Furnace Size Calculator. Quick BTU estimate by square footage and climate zone.
Choosing the right furnace size for your home is crucial to maintaining comfort and energy efficiency. Oversized or undersized units can lead to higher utility bills and uneven heating. That’s why we created the Furnace Size Calculator a simple tool to help homeowners accurately estimate the BTU (British Thermal Unit) rating needed for their living space. Whether you need a gas furnace size calculator or an electric furnace size calculator, this tool will guide you to the perfect match.
Furnace size is measured in BTUs, which indicates how much heat a furnace can produce in an hour. A correctly sized furnace ensures that your home is heated efficiently without overworking the system. An oversized furnace may cycle on and off too frequently, while an undersized one will struggle to maintain the desired temperature.
To calculate the furnace size for your home, you can follow a general formula based on square footage and climate zone. Here's a simplified method commonly used:
Furnace Size (BTU) = Home Square Footage × BTUs Needed Per Square Foot
The typical BTUs needed per square foot vary by region:
Example:
If you live in a moderate climate and your home is 2,000 sq ft:
Furnace Size = 2,000 × 45 = 90,000 BTU
This means you would need a furnace rated around 90,000 BTU for optimal performance.
| Home Size (sq ft) | Warm Climate (BTU) | Moderate Climate (BTU) | Cold Climate (BTU) |
|---|---|---|---|
| 1,200 | 36,000 – 42,000 | 48,000 – 54,000 | 60,000 – 72,000 |
| 1,500 | 45,000 – 52,500 | 60,000 – 67,500 | 75,000 – 90,000 |
| 2,000 | 60,000 – 70,000 | 80,000 – 90,000 | 100,000 – 120,000 |
| 2,200 | 66,000 – 77,000 | 88,000 – 99,000 | 110,000 – 132,000 |
| 2,500 | 75,000 – 87,500 | 100,000 – 112,500 | 125,000 – 150,000 |
The result will give you an accurate BTU recommendation for the size of furnace your home needs.
Choosing the right furnace size is a critical step for any homeowner. Our Furnace Size Calculator makes it simple to estimate the ideal BTU range based on your home’s square footage and location. Avoid common mistakes by using this easy-to-use tool before making a purchase decision. Whether you're upgrading your existing system or building a new home, this calculator ensures your comfort through every season.
Neither is ideal. Oversized units waste energy and cycle too quickly, while undersized units struggle to maintain temperature.
Yes. This calculator works for both types, but efficiency ratings (AFUE) can slightly affect final BTU needs.
While this calculator gives you a solid estimate, it's always wise to have a licensed HVAC technician confirm the results with a Manual J Load Calculation.
Insulation, window types, ceiling height, and home layout also impact heating requirements.