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Commercial Kitchen Exhaust-Hood Calculator


Review the methodology to ensure it aligns with your project's requirements.

Perform a separate analysis for each hood.

Refresh your web browser if the options are listed as: [Dynamic Dropdown] 

  1. Select English or Metric Units

  2. Select the Hood Description.  Hovering over the Hood Description dropdown menu will reveal ASHRAE hood descriptions.  

  3. Enter the project name (optional).

  4. Enter the hood designation (optional).

  5. Select the hood type.  Hovering over the Hood Type dropdown menu will reveal Hood Type descriptions from the IMC and FMC.     

  6. Select the first cooking appliance that will be served by the hood from the Cooking Equipment dropdown menu. 

  7. Enter the length of the cooling appliance.

  8. Click the "Click to add additional equipment" checkbox to add another piece of equipment that the hood will serve.  Repeat numbers 6 & 7.

  9. Repeat number 8 until all equipment under the hood has been entered.

  10. The results appear in the Summary Table.

  11. Enter the  % Make-up Air in the Summary Table (optional). 

Screenshot of Commercial Kitchen Hood Video

Wall-mounted canopy hoods are used for all types of cooking equipment located against a wall.


Single-island canopy hoods are used for all types of cooking equipment in a single-line island configuration.​


Double-island canopy hoods are used for all types of cooking equipment mounted back-to-back in an island configuration.


Back shelf/proximity hoods are used for counter-height equipment typically located against a wall, but possibly freestanding.


Pass-over hoods are used over counter-height equipment when pass-over configuration (from cooking side to serving side) is required.


Eyebrow hoods are used for direct mounting to ovens and some dishwashers.



Exhaust flow rates are determined by the hood style and the food service equipment served by the hood. Not all hoods are rated or designed for all cooking appliance types or duty ratings; therefore, cooking appliance type and duty rating must be included in the specification process. The following hood-type options are included in this calculator.  Descriptions are adapted from the 2019 ASHRAE Handbook, Chapter 34: 

In addition to Hood Style, Hood Type must be classified when designing a Commercial Kitchen Exhaust Hood.  Below are excerpts from the 2020 FMC & 2018 IMC describing Hood Type I and Hood Type II 

2020 FMC, Section 507.2,

Type I Hood: "Type I hoods shall be installed where cooking appliances produce grease or smoke as a result of the cooking process. Type I hoods shall be installed over medium-duty, heavy-duty, and extra-heavy-duty cooking appliances."

2020 FMC, Section 507.3,

Type II Hood: "Type II hoods shall be installed above dishwashers and appliances that produce heat or moisture and do not produce grease or smoke as a result of the cooking process, except where the heat and moisture loads from such appliances are incorporated into the HVAC system design or into the design of a separate removal system. Type II hoods shall be installed above all appliances that produce products of combustion and do not produce grease or smoke as a result of the cooking process. Spaces containing cooking appliances that do not require Type II hoods shall be provided with exhaust at a rate of 0.70 cfm per square foot (0.00033 m3/s). For the purpose of determining the floor area required to be exhausted, each individual appliance that is not required to be installed under a Type II hood shall be considered as occupying not less than 100 square feet (9.3 m2). Such additional square footage shall be provided with exhaust at a rate of 0.70 cfm per square foot [0.00356 m3/(s × m2)]."

The calculator uses CFM/linear foot of equipment values to calculate the total minimum volume of exhaust air. CFM/linear foot values are found in the International Mechanical Code (IMC), the Florida Mechanical Code (FMC), and the ASHRAE Handbook

Per the International Mechanical Code & Florida Mechanical Code:

The equipment with the heaviest duty under the hood will determine the exhaust volume for all the equipment.  For example, if a light-duty piece of equipment and a medium-duty piece of equipment are under one hood, the exhaust rate will be based on the requirements of medium-duty equipment. The length of the hood is the length of the equipment plus 12 inches. The make-up air is a percentage of the exhaust air. Hovering over this dropdown menu reveals notes from the International Mechanical Code and the Florida Mechanical Code.  This input is optional and only necessary if you want to calculate the volume of makeup air. The notes that appear are related to your project and are taken from the International Mechanical Code, the Florida Mechanical Code, and the ASHRAE Handbook. 

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