Grease Duct Velocity Calculator
Check grease duct velocity against code minimums.
Enter your values
ⓘ Live results
Results
- Duct velocity
- 1,350 FPM
- Duct area
- 1.78 sq ft
- Code minimum
- 1500 FPM (verify local minimum, some require 1800-2000)
- Status
- Below minimum — reduce duct size or add airflow
Quick answer
Grease ducts must maintain at least 1500 FPM (some jurisdictions require 1800-2000 FPM) to keep grease entrained and moving rather than settling in the duct.
Velocity = CFM / duct cross-sectional area
How to use the Grease Duct Velocity Calculator
- 1Enter the actual duct airflow (from balancing report or design).
- 2Enter the duct's internal width and height.
- 3Confirm velocity meets or exceeds your jurisdiction's minimum, typically 1500 FPM.
Worked example
Using the values the calculator loads with:
Inputs
- Duct airflow2400 CFM
- Duct width16 in
- Duct height16 in
Results
- Duct velocity1,350 FPM
- Duct area1.78 sq ft
- Code minimum1500 FPM (verify local minimum, some require 1800-2000)
- StatusBelow minimum — reduce duct size or add airflow
Frequently asked questions
What happens below minimum velocity?
Grease settles inside the duct instead of being carried to the filters/exhaust fan, creating a serious fire hazard.
Can duct be oversized instead?
No — oversized grease duct is a common code violation because it drops velocity below the self-cleaning threshold.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.