CFM Calculator
Estimate CFM airflow for exhaust fans and ventilation.
Estimate the CFM airflow required for exhaust fans and ventilation. The calculator uses room volume and air changes per hour (ACH): multiply the room volume in cubic feet by the target ACH, then divide by 60. For example, common ACH targets are 8 for bathrooms and 15 for kitchens.
Required CFM
128
fan airflow
Room volume
960
ft³
ACH used
8
bath 8, kitchen 15
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How does the cfm calculator work?
CFM = (room volume in ft³ × ACH) ÷ 60. Common ACH targets: bathrooms 8, kitchens 15, workshops 6, bedrooms 4.
What else do people ask about this calculator?
What CFM do I need for a bathroom?
Code minimum is 50 CFM, but sizing by 8 ACH keeps a large bathroom clear. A 10×8×8 ft bath needs ~85 CFM.
How is CFM calculated?
Multiply room volume by desired air changes per hour and divide by 60 minutes to get cubic feet per minute.
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