Home
Back
Duct Size Formula:
| From: | To: |
Duct size calculation is a critical aspect of HVAC system design that determines the appropriate cross-sectional area of air ducts based on airflow requirements and velocity constraints. Proper duct sizing ensures efficient air distribution and system performance.
The calculator uses the duct size formula:
Where:
Explanation: The formula calculates the required duct cross-sectional area by taking the square root of the ratio between airflow (CFM) and air velocity.
Details: Correct duct sizing is essential for maintaining proper air pressure, minimizing energy consumption, reducing noise levels, and ensuring adequate air distribution throughout the HVAC system.
Tips: Enter CFM (cubic feet per minute) and velocity (feet per minute) values. Both values must be positive numbers greater than zero for accurate calculation.
Q1: What is the typical velocity range for HVAC ducts?
A: Residential systems typically use 600-900 ft/min for supply ducts and 500-700 ft/min for return ducts. Commercial systems may use higher velocities.
Q2: How does duct size affect system performance?
A: Undersized ducts increase pressure drop and noise while reducing airflow. Oversized ducts increase installation costs and may cause air distribution issues.
Q3: What factors influence duct sizing besides CFM and velocity?
A: Duct material, layout complexity, number of bends, and static pressure requirements also affect final duct sizing decisions.
Q4: Should round or rectangular ducts be used?
A: Round ducts are more efficient for airflow but rectangular ducts are often used where space constraints exist. The calculator provides equivalent cross-sectional area.
Q5: How accurate is this calculation method?
A: This provides a basic calculation. Professional HVAC design should consider additional factors like friction loss, static pressure, and system-specific requirements.