Ventilation Fan Runtime Calculator
Estimate how many minutes per hour a ventilation fan must run to achieve a target air-change rate, plus daily energy use and cost.
Default project preview
38.1 minutes/hour
Room volume
2,700 ft³
Required average airflow
135 CFM
Delivered fan airflow
212.5 CFM
Continuous-fan ACH
4.72
Calculator
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Enter the project details and calculate a rounded material estimate.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Required average airflow = room volume × target ACH ÷ 60. Runtime fraction = required airflow ÷ delivered fan airflow. Daily energy = watts × runtime hours ÷ 1000.
FAQ
Ventilation Fan Runtime Calculator questions
What happens when runtime exceeds 60 minutes per hour?+
The entered fan is too small to reach the target air-change rate even when running continuously.
Why include delivered airflow efficiency?+
Duct resistance, grilles and installation conditions often reduce airflow below the fan free-air rating.
Is intermittent operation always acceptable?+
No. Required ventilation schedules and moisture control depend on the room use, contaminants and applicable standards.