Air Changes Per Hour Calculator

Calculate Air Changes Per Hour (ACH)

About Air Changes Per Hour

Air Changes Per Hour (ACH) measures how many times the air in a room is completely replaced per hour.

Formula:

ACH = (CFM × 60) / Room Volume

Where:

  • ACH = Air Changes Per Hour
  • CFM = Cubic Feet per Minute
  • Room Volume = Length × Width × Height

Recommended ACH Values:

• Living Room: 4-6 ACH
• Bedroom: 4-6 ACH
• Kitchen: 6-8 ACH
• Bathroom: 6-8 ACH
• Office: 6-8 ACH

Applications:

• HVAC system sizing
• Ventilation requirements
• Indoor air quality
• Energy efficiency planning

Proper air changes ensure good indoor air quality, comfort, and energy efficiency. Too few changes can lead to stale air, while too many can waste energy.