ACH = CFM × 60 ÷ room volume.
Enter realistic numbers from the property, equipment, job record, or company reports. Small input changes can produce large differences, so compare the estimate with actual performance.
Practical answers
What does ACH measure?
Air changes per hour estimates how many times the air volume of a room is replaced in one hour.
Can ACH be calculated from CFM?
Yes. Multiply airflow in CFM by 60 and divide by room volume in cubic feet.
Why can actual ACH differ?
Air leakage, pressure, duct losses, short-circuiting, measurement location, door position, and system operation can affect actual room performance.