HVAC Duct Size Calculator
Download a copy of our free HVAC duct size calculator and use it on the go to calculate your ideal duct size.
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Download our free HVAC duct size calculator today
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This calculator helps you determine the ideal duct size for your HVAC project. Ensure efficient airflow. Avoid system inefficiencies.
What Is an HVAC Duct Size Calculator?
An HVAC duct size calculator is a free online tool that helps determine the correct duct dimensions based on airflow rate and air velocity. Users simply select the duct shape; circular, rectangular, or square; and input:
– Airflow rate (CFM) – Cubic feet per minute of air the system needs to move
– Air velocity (FPM) – Feet per minute of desired airflow speed
The calculator then provides:
– Duct area (sq. in.)
– Diameter or side dimensions based on the selected shape
This ensures proper airflow distribution and system efficiency without requiring complex manual calculations.
Who Uses an HVAC Duct Size Calculator?
This tool is ideal for:
– HVAC technicians and contractors designing or installing ductwork
– Engineers and project managers verifying airflow specs
– Homeowners and business owners exploring HVAC upgrades or troubleshooting airflow issues
What Inputs Are Required?
To use the calculator, you’ll need:
– Duct shape: Circular, rectangular, or square
– Airflow rate (CFM)
– Air velocity (FPM)
Based on these, the tool calculates the required duct area and dimensions to maintain efficient airflow.
Why Is Duct Sizing Important in HVAC Systems?
Proper duct sizing ensures balanced airflow, reduces energy waste, minimizes noise, and improves overall comfort and system longevity.
What’s the Difference Between CFM and FPM?
– CFM (Cubic Feet per Minute) measures the volume of air moving through the system.
– FPM (Feet per Minute) measures the speed of that airflow. Both are essential for accurate duct sizing.
Can I Use This Calculator for Any Duct Shape?
Yes. The calculator supports circular, rectangular, and square duct shapes, making it versatile for various HVAC setups.
Even if math wasn’t exactly your favorite subject, we’ve made it easy for you. The formulas used in the calculator are:
– Area = (Flow Rate / Max Velocity) × (12 × 12)
– Circular Duct Diameter = sqrt(Area / 3.14) * 2
– Rectangular Duct Height = sqrt(Area / 2)
– Rectangular Duct Width = Area / Rectangular Duct Height
– Square Duct Size = sqrt(Area)