Air Changes per Hour Calculator

Inputs

Floor area (A)

Served room or zone floor area.

m²

Ceiling height (H)

Average clear height used to calculate room volume.

Target air changes (ACH_t)

Target air changes per hour for the room or process.

ACH

Design or measured airflow (Q)

Airflow supplied to, exhausted from or recirculated through the room.

m³/h

Default result

Required airflow(Q_req)

324m³/h

Pass

airflow for 6.00 ACH

Also computed

Actual air changes(ACH)6.667ACH

meets or exceeds the target air-change rate

Room volume(V)54m³

Minutes per change(t)0.15min

Method notes 3 notes

Room volume is floor area times average ceiling height.
ACH = airflow × 3600 / room volume. Required airflow = room volume × target ACH / 3600.
ACH is a room air-change screen, not a complete outdoor-air code calculation. For occupied-building ventilation, check the applicable ASHRAE 62.1/62.2 or local-code method.