Grow Room Fan & Ventilation Calculator Australia
Grow Room Fan & Ventilation Calculator Australia
Calculate the airflow required for a grow tent or indoor growing space using room volume, air-exchange rate and sensible heat load.
The result is the delivered airflow your room requires — not simply the advertised maximum airflow you should look for on a fan box. Carbon filters, ducting, bends and intake restrictions are accounted for in the next stage of the calculator.
Enter the actual dimensions, electrical heat load and temperature conditions below. The calculator compares the air-exchange requirement with the airflow required to remove sensible heat and uses the larger result.
Grow Room Ventilation Calculator
Calculate the minimum delivered airflow before accounting for carbon-filter and duct-system resistance.
Room Dimensions
Ventilation Requirement
Temperature Conditions
How to Calculate Grow Room Airflow
Grow-room fan sizing starts with the airflow the room actually needs. Three simple calculations determine the initial requirement.
Calculate Room Volume
Use the actual internal dimensions of the tent or room.
Calculate Air Exchange
This gives a basic ventilation baseline.
Calculate Heat Removal
The smaller the temperature difference between intake and room air, the more airflow is required.
Use the Larger Requirement
This becomes the delivered airflow target for the fan and duct system.
The result above tells you how much airflow needs to reach the room. The next step is to account for the resistance created by the carbon filter, ducting, bends, intake and other components before choosing the fan.
Grow Tent Fan Size Guide
The table below gives a simple air-exchange baseline for common grow tent sizes. It assumes a 2 m internal height and one complete air exchange every two minutes.
Heat load, intake temperature, carbon filters, ducting and system resistance can increase the required airflow substantially. Use the calculator above for your actual setup.
| Tent Size | Assumed Height | Volume | 2-Minute Air Exchange | Common Duct Range |
|---|---|---|---|---|
| 60 × 60 cm | 2.0 m | 0.72 m³ | 22 m³/h | 100 mm |
| 60 × 120 cm | 2.0 m | 1.44 m³ | 43 m³/h | 100–125 mm |
| 90 × 90 cm | 2.0 m | 1.62 m³ | 49 m³/h | 125–150 mm |
| 100 × 100 cm | 2.0 m | 2.00 m³ | 60 m³/h | 125–150 mm |
| 120 × 120 cm | 2.0 m | 2.88 m³ | 86 m³/h | 150 mm |
| 150 × 150 cm | 2.0 m | 4.50 m³ | 135 m³/h | 150–200 mm |
| 120 × 240 cm | 2.0 m | 5.76 m³ | 173 m³/h | 200–250 mm |
The duct ranges above are practical starting points rather than fixed rules. The final diameter should be checked against the airflow your room actually requires.
Grow Room Fan Sizing Examples
These examples show why heat load can matter much more than the physical volume of the tent.
Assume a 60 × 60 × 160 cm tent, 150 W sensible heat load and intake air 4°C cooler than the desired room temperature.
The heat calculation governs, so the initial target is approximately 110 m³/h delivered airflow.
Assume a 120 × 120 × 200 cm tent, 500 W sensible heat load and a 4°C difference between intake and target temperature.
The initial target becomes approximately 366 m³/h delivered airflow.
Assume a 3 × 3 × 2.4 m room, 2400 W sensible heat load and a 4°C difference between intake and target temperature.
At this scale the heat load dominates. Larger rooms should also be assessed for duct resistance, humidity and active cooling requirements.
When Ventilation Is Not Enough
An exhaust fan can only use the air available at the intake.
If the intake air is as warm as, or warmer than, the desired room temperature, increasing exhaust airflow cannot provide the sensible cooling required to hold that temperature.
Humidity has a similar limitation. Ventilation only provides net moisture removal when the incoming air contains less water vapour than the room condition you are trying to maintain.
Grow Room Ventilation Guides
The calculator gives you the airflow requirement. Use the detailed guides below when you need to design a particular part of the system.
Grow Room Carbon Filter Guide
Learn how filter airflow ratings, pressure drop, contact time, prefilters and fan matching affect a filtered exhaust system.
Read the Carbon Filter Guide →Grow Room Ducting Guide
Choose duct diameter and understand flexible duct, bends, reducers, Y-pieces and system resistance.
Read the Ducting Guide →Intake & Negative Pressure Guide
Understand passive intake, active intake, replacement-air requirements and negative room pressure.
Read the Intake Guide →Grow Room Temperature & Cooling Guide
Understand heat load, intake-air temperature, ventilation cooling limits and when active cooling becomes necessary.
Read the Cooling Guide →Grow Room Humidity & Dehumidification Guide
Understand RH, humidity ratio, dew point, moisture removal, transpiration and dehumidifier selection.
Read the Humidity Guide →Grow Room Ventilation in Brisbane
See how Brisbane temperature and humidity affect ventilation performance throughout the year.
Read the Brisbane Guide →Grow Room Fan Noise & Silencer Guide
Reduce aerodynamic, ductborne and vibration noise using better duct design, fan control and acoustic equipment.
Read the Noise Guide →Environmental Controller Guide
Learn how temperature, humidity, VPD, sensor placement and variable-speed fan automation fit into the ventilation system.
Read the Controller Guide →Grow Room Ventilation Troubleshooting
Diagnose weak airflow, excessive negative pressure, high temperature, humidity problems and carbon-filter issues.
Read the Troubleshooting Guide →Shop Grow Room Ventilation
Once you know the airflow your space requires, build the system around the correct fan, filter, ducting and environmental controls.
Shop inline fans, circulation fans and grow-room ventilation equipment.
Shop VentilationShop ducting, connectors and airflow accessories across common grow-room diameters.
Shop DuctingShop AC Infinity inline fans, carbon filters, circulation fans and UIS environmental controllers.
Shop AC InfinityCompare grow tent sizes and calculate the ventilation requirement from the actual dimensions.
Shop Grow TentsExplore dehumidifiers and other environmental equipment for conditions that ventilation alone cannot manage.
Shop Environmental EquipmentSend us your room dimensions, lighting wattage and basic duct layout and we can help you narrow down the system.
Contact Green GeniusGrow Room Fan Calculator FAQs
What size exhaust fan do I need for my grow room?
Calculate the airflow required from room volume and heat load, then select a fan capable of delivering that airflow against the resistance created by the carbon filter, ducting and intake system.
How do I calculate grow room airflow?
Start with room volume and your desired air-exchange interval. Then calculate the airflow required to remove the sensible heat load. Use whichever requirement is higher.
How often should air be exchanged in a grow tent?
A full exchange approximately every one to three minutes is a useful starting range for many ventilated tents, but heat and humidity can require substantially more airflow.
Does a carbon filter reduce fan airflow?
Yes. Air passing through the carbon bed and prefilter experiences resistance, so the fan will normally deliver less airflow than its low-pressure or free-air maximum.
See the Grow Room Carbon Filter Guide for detailed fan and filter matching.
Do ducting and bends reduce airflow?
Yes. Straight duct creates friction and fittings such as bends, reducers and Y-pieces create additional pressure losses. Small duct and compressed flexible duct can make those losses substantially worse.
See the Grow Room Ducting Guide .
Do I need an intake fan?
Not always. Many grow tents can operate with adequately sized passive intake openings. Active intake becomes more useful when the replacement-air path is long or restrictive, or when a larger room requires deliberate supply airflow.
Can an exhaust fan reduce humidity?
Only when the incoming replacement air is sufficiently drier than the room condition. Relative humidity alone is not enough to determine this because temperature also affects RH.
Can an exhaust fan cool below the intake-air temperature?
Ventilation alone cannot reliably maintain the room below the dry-bulb temperature of the air entering it. If the intake air is already too warm, active cooling or a cooler intake source is required.
Need Help Choosing a Ventilation System?
Use the calculator above first, then send Green Genius your room dimensions, lighting wattage, proposed carbon filter, duct size and approximate duct route. We can help you compare suitable ventilation equipment.