Grow Tent CFM Calculator
Inline fan size for a grow tent with filter losses.
Enter your values
ⓘ Live results
Results
- Fan size to buy
- 190 CFM
- Base tent volume
- 104 cu ft (one exchange per minute)
- Total uplift applied
- 65%
- Suggested duct
- 4 in
- Passive intake area
- 57 sq in minimum
Working
- 1104 cu ft x 1.65 = 172 CFM
Quick answer
A grow tent should exchange its full air volume every one to three minutes, then add allowances for the carbon filter, ducting and light heat.
CFM = tent volume x (1 + filter% + duct% + heat%)
How to use the Grow Tent CFM Calculator
- 1Enter your tent's footprint and height in feet.
- 2Say whether you run a carbon filter and how many bends the ducting has.
- 3Add the light wattage so heat removal is included, then buy the next fan size up with a speed controller.
Worked example
Using the values the calculator loads with:
Inputs
- Tent length4 ft
- Tent width4 ft
- Tent height6.5 ft
- Carbon filterYes
- Light wattage600 W
- Number of duct bends2
Results
- Fan size to buy190 CFM
- Base tent volume104 cu ft (one exchange per minute)
- Total uplift applied65%
- Suggested duct4 in
- Passive intake area57 sq in minimum
- 104 cu ft x 1.65 = 172 CFM
Frequently asked questions
What size fan for a 4x4 tent?
Around 200–260 CFM with a carbon filter and 600 W of light — a 6 inch inline fan is the usual choice.
Should the fan run constantly?
Yes during lights-on; many growers drop to a lower speed at night to hold humidity.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.