Ventilation estimator
How to Size an Inline Fan for a Grow Tent
Reviewed 2026-07-21
Quick answer
Tent volume divided by the desired exchange interval gives a base CFM—not the final fan. Add planning headroom for every restriction and confirm the installed path against temperature, humidity, noise, and manufacturer performance data.
Make the decision
Try the planning tool.
Inputs stay in your browser. Nothing is saved or sent.Starting selection range
40–54 CFMFilters, bends, duct, intake, heat, and fan curves can move the real requirement.01
Start with volume, not a fan badge
Multiply length, width, and height. Dividing by an exchange interval creates a clean-air starting point.
02
The installed air path always matters
Filters, tight bends, long duct, undersized intake, screens, and heat load reduce useful performance. Add planning headroom rather than pretending the base number is exact.
03
A 2x4x5 tent contains 40 cubic feet
A one-minute base exchange starts at 40 CFM. The real selection must then reflect the filter, duct, intake, heat, and desired control range.
04
Ventilation components for a 2x4 tent
This 190 CFM fan is a candidate with speed-control room, not a promise of installed airflow or climate control.
05
Common sizing mistakes
A free-air rating describes a test point, not the completed grow room.
- Ignoring the carbon filter
- Using several tight bends
- Providing too little intake area
- Exhausting into the same enclosed space
- Running full speed because no control range was planned
FAQs
Questions growers ask before the next step.
Is 190 CFM enough for a 2x4 tent?
It may provide substantial headroom over the 40-cubic-foot base volume, but installed performance depends on the filter, ducting, intake, heat, and room receiving the exhaust.
Should the tent walls pull inward?
A slight inward pull can indicate negative pressure. Severe collapse suggests the intake or air path may be overly restricted.
Sources and boundaries
The calculator is an estimator with visible assumptions, not a fan-performance guarantee.Current product specifications come from the reviewed catalog.