Island Hood CFM Calculator
Exhaust airflow for an island kitchen hood.
Enter your values
Enter the hood length in ft.
Choose one of: Light duty, Medium duty, Heavy duty, Extra heavy / solid fuel.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Exhaust airflow
- 3,200 CFM
- Rate used
- 400 CFM/ft
- Makeup air (90%)
- 2,880 CFM
- Duct at 1800 FPM
- 1.78 sq ft
- Round duct dia
- 18.1 in
Quick answer
Island canopy hoods are sized at 250-700 CFM per linear foot of hood depending on appliance duty, roughly 50% more than an equivalent wall hood.
CFM = hood length x CFM per linear foot (island rate)
At a glance
| What it does | Exhaust airflow for an island kitchen hood. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Hood length, Appliance duty |
| Main output | Exhaust airflow |
| Formula | CFM = hood length x CFM per linear foot (island rate) |
| Cost | Free — no sign-up, no download |
How to use the Island Hood CFM Calculator
- 1Measure hood length over the cooking equipment.
- 2Pick the heaviest appliance duty beneath the hood.
- 3Provide tempered makeup air at 85-95% of exhaust to avoid depressurising the kitchen.
Inputs explained
- Hood length(ft)
- Enter the hood length in ft.
- Appliance duty
- Choose one of: Light duty, Medium duty, Heavy duty, Extra heavy / solid fuel.
Worked example
Using the values the calculator loads with:
Inputs
- Hood length8 ft
- Appliance dutyMedium duty
Results
- Exhaust airflow3,200 CFM
- Rate used400 CFM/ft
- Makeup air (90%)2,880 CFM
- Duct at 1800 FPM1.78 sq ft
- Round duct dia18.1 in
Frequently asked questions
Why do island hoods need more air?
There are no side walls to contain the thermal plume, so cross-drafts pull effluent out from all four sides.
Can I add side panels?
Yes — end panels or a valance can cut required CFM by capturing more of the plume.
What do I need to enter into the Island Hood CFM Calculator?
Just 2 values: hood length, appliance duty. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Island Hood CFM Calculator work out the answer?
Island canopy hoods are sized at 250-700 CFM per linear foot of hood depending on appliance duty, roughly 50% more than an equivalent wall hood. It applies the formula CFM = hood length x CFM per linear foot (island rate) and shows the working so you can check each step by hand.
Is the Island Hood CFM Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.