CFM Calculator — Room Ventilation Airflow

How the cfm calculator works

CFM = (room volume in ft³ × ACH) ÷ 60. Common ACH targets: bathrooms 8, kitchens 15, workshops 6, bedrooms 4.

Code minimum is 50 CFM, but sizing by 8 ACH keeps a large bathroom clear. A 10×8×8 ft bath needs ~85 CFM.

Multiply room volume by desired air changes per hour and divide by 60 minutes to get cubic feet per minute.

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