Air Changes Per Hour Calculator
Ventilation rate for a room.
Enter your values
Results update instantly as you type — no submit needed.
Results
- Air changes per hour
- 5.56
- Room volume
- 2,700 ft³
- CFM for target ACH
- 270
- Status
- Below target
Quick answer
Air changes per hour measures how many times a room's air volume is replaced each hour.
ACH = CFM × 60 ÷ room volume
How to use the Air Changes Per Hour Calculator
- 1Enter the room dimensions.
- 2Enter the measured or designed airflow.
- 3Set the ACH target for the room type.
Frequently asked questions
What ACH does a kitchen need?
Typically 7–8; bathrooms 6–8 and offices 4–6.
Does higher ACH cost more?
Yes — in fan energy and conditioned air lost.