Air Changes per Hour Calculator

Find ACH from room volume and air flow.

Air changes per hour (ACH) 9

Formula: ACH = CFM × 60 ÷ room volume

Step-by-step with your numbers:

1. Values used:

2. Room volume = 1,000

3. Air flow = 150 CFM

5. Air changes per hour = 9ACH

Did we solve your problem today?

ACH measures how many times room air is replaced each hour.

The math behind it

ACH = CFM × 60 ÷ room volume (ft³). Residential rooms typically need 2–6 ACH.

1,000 ft³ with 150 CFM → 9 ACH.

Why 60?

CFM is cubic feet per minute; multiply by 60 for per-hour.