Furnace Size Calculator – BTU (Heating) Estimation
Selecting the-right-furnace-size is important in terms of efficient heating, reduced energy costs, and comfort in the home. Our Furnace Size Calculator can assist you in selecting the proper heating capacity (measured in BTUs, or British Thermal Units) for your home based upon its size, insulation level, and location.
Furnace BTU Calculator
Calculate the required BTU for furnace heating based on room dimensions, climate, and insulation type:
Why Furnace Size Matters?
If your furnace is undersized, it will not be able to keep your home warm in the winter. If your furnace is oversized, it will short-cycle (turning on and off again very quickly), which adds to your energy costs and shortens the life of the equipment.
Furnace BTU Chart: General Guidelines
A furnace BTU chart provides a quick reference for rating BTU output according to the square footage and climate of your home. A typical example works like this:
This chart provides a starting point for finding the BTU input, but to get precise calculations, use a calculator that estimates the BTU input.
How to Calculate the Right Furnace Size
We calculate furnace size using the following formula:
BTU = Square Feet × Heating Factor (based on climate)
Heating Factors by Climate Zone:
Climate Zone | Heating Factor (BTU/sq ft) |
---|---|
Hot (South Florida, Texas) | 30–35 |
Moderate (California, Tennessee) | 40–45 |
Cold (Chicago, New York) | 50–60 |
Very Cold (Minnesota, Canada) | 60–70 |
What You’ll need to utilise this calculator:
- Size of house (in sq ft or m²)
- Location or climate zone
- Insulation value (basic/standard/high)
- Desired temperature inside the house
Furnace efficiency is important
Modern furnaces using AFUE (annual fuel utilization efficiency):
- Standard efficiency = 80%
- High efficiency = 90–98%
Example: If your furnace is rated at 90% AFUE and you require 100,000 BTU of heat, you’ll want a furnace that produces 111,000 BTU input.
Overall, our calculator has the following functions:
- Smart climate-zone adjustment
- Calculated BTU estimate based on heating factor
- Suggestions for furnace size in input and output BTU.
- For gas, electric, and oil furnaces
- Operations include efficiency consideration.
Tips From The Pros:
- Always consult a HVAC contractor before installation.
- Improve insulation to minimize furnace size and energy usage.
- Seal windows and doors to keep heat in.
Local Based Outcomes
This tool provides you area/region-specific outcomes whether you live in the freezing Midwest or temperate Southern states.
Final Thoughts:
Determining your furnace size is not guesswork-it is science so Utilize our free Furnace Size Calculator to get instant scene-specific outcomes based on your home and area location.
FAQ: Frequently Asked Questions
Q: How large of a furnace do I need for 1,500 square feet?
A: Likely between 60,000 and 90,000 BTUs depending on insulation ratings, and climate zone.
Q: Is a bigger Furnace size always better?
A: No. Oversized units can create temperature swings, and higher bills from short-cycling.
Q: Can I determine furnace size in kilowatts (kW)?
A: Yes, to convert BTU/hr to kW, just take the BTU value and divide by 3,412.