TenorOpsRestaurant & Kitchen Operations · Kitchen Mechanical
Free Commercial Kitchen Exhaust Hood CFM & Make-Up Air Calculator
Calculate required commercial kitchen exhaust hood airflow (CFM) and make-up air replacement volume by hood style, linear footage, and cooking duty class.
Hood Style & Cooking Line
Kitchen Hood CFM Inputs
Ventilation Results
Exhaust & Make-Up Air CFM
Step-by-step guide
How to Use the Commercial Kitchen Hood CFM Calculator
- 1Select hood style and cooking equipment duty class
Choose Wall Canopy, Single Island, Double Island, or Backshelf and Light, Medium, Heavy, or Extra-Heavy duty.
- 2Enter hood length in linear feet
IMC code specifies exhaust CFM per linear foot of hood based on duty class and mounting style.
- 3Review Required Exhaust CFM and Make-Up Air CFM
Size your rooftop exhaust fan and tempered make-up air unit accurately.
Formula & methodology
IMC Commercial Kitchen Hood Airflow Guidelines
Exhaust CFM = Hood Linear Feet × Duty Class CFM/ft × Hood Style Factor Make-Up Air CFM = Exhaust CFM × (Make-Up Air % ÷ 100, typically 80%–90%)
Keeping make-up air at 80%–90% of exhaust maintains slight negative pressure in the kitchen so cooking smoke and odors never drift into the dining room.
Common questions
Frequently Asked Questions
Why should a commercial kitchen have 80%–90% make-up air?
Supplying 85% make-up air keeps the kitchen slightly negative relative to the dining room, preventing grease vapor from entering guest areas while avoiding slammed doors or back-drafted water heaters.
What is the difference between a Type I and Type II kitchen hood?
Type I hoods include grease baffles and fire suppression for appliances that produce grease and smoke (fryers, griddles, broilers); Type II hoods collect heat and steam from dishwashers and ovens.
Why do island canopy hoods require more CFM than wall-mounted hoods?
Island hoods are open on all four sides and subject to cross-drafts, requiring 30%–50% higher exhaust volume to capture rising thermal plumes.
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