HVAC Duct Sizing Calculator
Quickly determine the proper duct size based on airflow requirements, or calculate the airflow capacity of existing ductwork for both round and square ducts.
Created by Sam Ruf
Duct Sizing Calculator
Enter your parameters below to calculate proper duct sizes or airflow capacity.
Results
Your calculation results will appear here.
Recommended Duct Velocities
Proper duct velocities balance airflow requirements, noise considerations, and energy efficiency. Here are some general guidelines:
- Residential Supply Branches: 500-700 FPM
- Residential Main Supply Trunk: 700-900 FPM
- Residential Return Air: 500-700 FPM
- Commercial Supply: 1000-1300 FPM
- Commercial Return: 800-1000 FPM
- Industrial Applications: 1300-1800 FPM
Lower velocities result in quieter operation but require larger ducts. Higher velocities allow for smaller ducts but generate more noise and resistance.
Important Note
This calculator provides estimates based on standard formulas. For final system design, consider factors such as system static pressure, fittings, transitions, turns, and equipment specifications. Always consult with a qualified HVAC professional for complex installations.