Duct Diameter Calculator
Calculate optimal duct diameter for your dust collection system based on CFM requirements and target air velocity.
System Parameters
Cubic feet per minute needed
Optimal range: 3500-4000 FPM
Recommended Duct Size
Enter CFM and velocity requirements to calculate optimal duct diameter.
Standard Duct Sizes
2.5"Up to 150 CFM
3"150-250 CFM
4"250-400 CFM
5"400-650 CFM
6"650-900 CFM
8"900-1500 CFM
Duct Sizing Guide
Air Velocity
Proper air velocity is critical for dust transport:
- 3500-4000 FPM: Optimal range
- <3000 FPM: Dust may settle
- >4500 FPM: Excessive noise/wear
- Higher velocity = smaller duct
Duct Sizing Formula
Diameter = √(CFM × 183.3 / Velocity)
- CFM = Cubic feet per minute
- Velocity = Feet per minute (FPM)
- Result in inches
- Round up to nearest standard size
Round vs Rectangular
- Round: Most efficient, less friction
- Rectangular: Fits tight spaces
- Round preferred for main runs
- Rectangular for drops/branches
Design Tips
- Use largest practical duct size
- Minimize elbows and bends
- Maintain velocity throughout system
- Use smooth-wall ducting
- Seal all connections