Cannabis Grow Room Airflow Calculator
Circulation and exhaust CFM for a cannabis grow room.
Enter your values
Enter the room length in ft.
Enter the room width in ft.
Enter the ceiling height in ft.
Enter the total lighting load in W.
Enter the allowable temp rise in F.
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.
- Internal circulation airflow
- 1,500 CFM
- Exhaust airflow for lighting heat
- 1,896 CFM
- Room volume
- 3,000 cu ft
Quick answer
Cannabis grow rooms need internal air circulation of about 1 full room air exchange every 1-3 minutes plus exhaust sized to the lighting heat load.
Circulation CFM = volume / exchange time (min); Exhaust CFM = (W x 3.412)/(1.08 x dT)
At a glance
| What it does | Circulation and exhaust CFM for a cannabis grow room. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Room length, Room width, Ceiling height, Total lighting load, Allowable temp rise |
| Main output | Internal circulation airflow |
| Formula | Circulation CFM = volume / exchange time (min); Exhaust CFM = (W x 3.412)/(1.08 x dT) |
| Cost | Free — no sign-up, no download |
How to use the Cannabis Grow Room Airflow Calculator
- 1Compute room volume for circulation fan sizing (aim for a 1-3 minute full exchange).
- 2Total the wattage of grow lights and other heat-producing equipment.
- 3Convert that heat load to exhaust CFM at your allowable temperature rise.
Inputs explained
- Room length(ft)
- Enter the room length in ft.
- Room width(ft)
- Enter the room width in ft.
- Ceiling height(ft)
- Enter the ceiling height in ft.
- Total lighting load(W)
- Enter the total lighting load in W.
- Allowable temp rise(F)
- Enter the allowable temp rise in F.
Worked example
Using the values the calculator loads with:
Inputs
- Room length20 ft
- Room width15 ft
- Ceiling height10 ft
- Total lighting load6000 W
- Allowable temp rise10 F
Results
- Internal circulation airflow1,500 CFM
- Exhaust airflow for lighting heat1,896 CFM
- Room volume3,000 cu ft
Frequently asked questions
Do I need CO2 supplementation ventilation separately?
Yes — CO2-enriched rooms should minimize outdoor air exchange during light hours except for heat removal.
Dehumidification?
Flowering stage transpiration adds a large latent load — size dehumidifiers separately from sensible cooling.
What do I need to enter into the Cannabis Grow Room Airflow Calculator?
Just 5 values: room length, room width, ceiling height, total lighting load, allowable temp rise. 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 Cannabis Grow Room Airflow Calculator work out the answer?
Cannabis grow rooms need internal air circulation of about 1 full room air exchange every 1-3 minutes plus exhaust sized to the lighting heat load. It applies the formula Circulation CFM = volume / exchange time (min); Exhaust CFM = (W x 3.412)/(1.08 x dT) and shows the working so you can check each step by hand.
Is the Cannabis Grow Room Airflow 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.