Commercial Hood CFM Calculator
Use this tool to determine the minimum exhaust flow rate (CFM) for a Type I commercial canopy hood based on IMC guidelines, considering hood length, mounting type, and appliance duty.
| Duty | Rate (CFM/ft) |
|---|
Introduction
For HVAC engineers and kitchen-exhaust designers sizing a Type I canopy hood who need the IMC minimum exhaust rate fast, the catch being that the required CFM per linear foot depends on both how the hood is mounted and how heavily the appliances under it are used. This Commercial Hood CFM Calculator simplifies the process, quickly providing the minimum exhaust flow rate based on hood length, type, and appliance duty, according to the International Mechanical Code (IMC) standards for unlisted Type I canopy hoods.
This tool utilizes the IMC minimum exhaust rates for unlisted Type I canopy hoods, which depend on appliance duty: wall-mounted 200/300/400/550 CFM per ft and single island 400/500/600/700 CFM per ft (light, medium, heavy, extra-heavy).
How to Use This Tool
- Enter the hood length in feet in the length field (decimals allowed, e.g. 8.5).
- Select the hood type: wall-mounted canopy or single island canopy.
- Select the appliance duty: light, medium, heavy, or extra-heavy.
- Read the minimum exhaust flow rate in CFM and check the formula line against the highlighted rate in the table.
FAQ
Q: How many CFM does a 10-foot commercial hood need?
A: It depends on mounting and duty: 10 ft of wall-mounted canopy needs 2,000 / 3,000 / 4,000 / 5,500 CFM at light / medium / heavy / extra-heavy duty, and 10 ft of single island canopy needs 4,000 / 5,000 / 6,000 / 7,000 CFM at the same duties.
Q: What exhaust rates does the IMC set for unlisted Type I canopy hoods?
A: For unlisted Type I canopy hoods the minimum is 200 / 300 / 400 / 550 CFM per linear ft for wall-mounted canopies and 400 / 500 / 600 / 700 CFM per linear ft for single island canopies, at light / medium / heavy / extra-heavy appliance duty respectively.
Q: Does an island canopy hood really need more CFM than a wall-mounted one?
A: Yes — at every duty level the single island rate is higher: 400 vs 200 CFM/ft at light, 500 vs 300 at medium, 600 vs 400 at heavy, and 700 vs 550 at extra-heavy.
Q: What if my hood is a listed hood rather than an unlisted canopy?
A: This calculator applies the IMC minimums for unlisted Type I canopy hoods; a listed hood follows its listing, so use the manufacturer's listed minimum instead of this figure.