This furnace size calculator, or furnace BTU calculator, will help you determine what size of furnace you need for any room area, insulation type, or outdoor temperature.

After the furnace sizing calculation, you’ll find how the size of the furnace is calculated. We also made 3 examples for: What size furnace do I need for a 1000 sq ft house? (Example 1) What …

Our furnace size calculator delivers a personalized BTU (British Thermal Unit) estimate by analyzing your home’s square footage, climate zone, windows, insulation, and more—based …

Jun 3, 2025 · This furnace size calculator uses your house size, climate (see the map below) and other important information to tell you what size furnace your home needs to keep it warm …

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 …

Dec 22, 2025 · Use our free tool furnace size calculator to determine the right furnace BTU for your home based on square footage, climate, and insulation.

Nov 20, 2025 · Our furnace size calculator makes it easy to estimate how many BTUs you’ll need based on your home’s location, square footage, and the age of your windows and insulation.

Calculate the right furnace size for your home with our free Furnace Size Calculator. Enter your home measurements and get instant furnace size recommendations.

Determines appropriate furnace capacity based on heating load.

This calculator eliminates guesswork by providing precise furnace sizing calculations based on square footage, ceiling height, climate zone, insulation quality, and windows, helping you …