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Commercial Kitchen Hood CFM Calculator

Estimate how much air a commercial kitchen hood needs to exhaust based on its style (wall canopy, island, backshelf), its length and the heaviest appliance under it — plus a starting point for makeup air and duct size.

Hood
Size
ft
ft
0 uses the appliance line plus a 6 in. overhang at each end.

Results

Estimated exhaust airflow3,300 CFMWall-mounted canopy, medium duty, 300 CFM per ft
Hood length used11 ft
Makeup air (≈85%)2,810 CFM
Round duct at 1,800 fpm≈ 19 in
Minimum hood length (6 in overhang each end)
11 ft
Exhaust per linear foot
300 CFM/ft
Duct cross-section
264 in² (1.83 ft²)

Planning estimate. Listed hoods (UL 710) are usually approved at the lower airflow in their listing, and current codes, the manufacturer, a mechanical engineer and your local authority determine the final exhaust and makeup air design.

Grease duct, fire suppression, clearances and makeup air tempering are governed by the mechanical code and NFPA 96 as adopted locally.

How it works

  1. Choose the hood style and the duty of the heaviest appliance under it.
  2. Enter the length of the appliance line, and the hood length if you already know it.
  3. Read the exhaust CFM, an approximate makeup air requirement and a rough duct diameter.
  4. Share the numbers with your hood supplier or mechanical engineer as a starting point.

Formula

Exhaust CFM = CFM per linear foot × hood length (× 2 for double island)
Hood length ≥ appliance line + 6 in. at each end
Makeup air ≈ 85% of exhaust
Duct area = CFM ÷ 1,800 fpm → round diameter

CFM per foot for unlisted Type I hoods (IMC 2009 §507.13): wall canopy 200 / 300 / 400 / 550 for light, medium, heavy and extra-heavy duty; single island 400 / 500 / 600 / 700; double island 250 / 300 / 400 / 550 per side; backshelf 250 / 300 / 400; eyebrow 250 for light and medium only. Makeup air is commonly designed at about 80–90% of exhaust so the kitchen stays slightly negative. Grease ducts typically run at 1,500–2,500 fpm; 1,800 fpm is used here.

Example

A burger restaurant with a gas charbroiler, two fryers and a griddle in a 12 ft line under a 13 ft wall-mounted canopy hood.

Inputs

Hood style
Wall-mounted canopy
Heaviest appliance duty
Heavy — gas charbroilers, woks
Length of appliance line
12 ft
Hood length (optional)
13 ft

Result

Estimated exhaust airflow5,200 CFMWall-mounted canopy, heavy duty, 400 CFM per ft
Hood length used13 ft
Makeup air (≈85%)4,420 CFM
Round duct at 1,800 fpm≈ 24 in
Load this example into the calculator →

Why duty and hood style matter

The heaviest appliance sets the duty for the whole hood: a single charbroiler in a line of ovens makes it a heavy-duty hood. Island hoods need more air than wall hoods because there is no wall to contain the plume, and cross-drafts pull smoke away more easily.

Most commercial hoods sold today are listed (UL 710) and tested to capture at lower airflow than the prescriptive table. The manufacturer’s listing, not this table, will usually set the final CFM — often saving on fan energy and makeup air heating.

Planning only

Kitchen ventilation is a life-safety system. Final design, including fire suppression, grease duct construction, clearances and makeup air, must follow the codes adopted locally and be confirmed by the hood manufacturer, a qualified engineer and the authority having jurisdiction.

Frequently asked questions

How many CFM per foot for a commercial kitchen hood?

Under the older prescriptive IMC table, a wall canopy needs 200–550 CFM per foot depending on appliance duty, and a single island canopy 400–700. Listed hoods often run lower.

How much makeup air does a restaurant hood need?

Usually close to the exhaust volume — commonly 80–90% delivered through the hood or HVAC, with the building balanced so the kitchen stays slightly negative.

What duty is a fryer?

Fryers, griddles and open-burner ranges are typically classed as medium duty. Gas charbroilers and woks are heavy duty; solid-fuel appliances are extra heavy.

Can I use this for permit drawings?

No. It is a planning estimate. Permit design must follow local codes and the hood’s listing.