This building-airflow calculator estimates room volume and hourly air exchange rate from floor area, ceiling height, and airflow.
Construction
Air Changes per Hour Calculator
Calculate room volume and hourly air changes from dimensions and airflow.
Calculator
About this calculator
Formula notes
volume = floor area x height; air changes per hour = airflow in cubic metres per minute x 60 / volume.
Worked examples
- Example: 50 m2 with 2.5 m ceiling and 10 m3/min ventilation has volume 125 m3 and 4.8 air changes per hour.
- A 1,000 sq ft room with an 8 ft ceiling and 800 cfm airflow has 8,000 cu ft volume and 6.0 air changes per hour.
How to use it
- Enter floor area and ceiling height.
- Enter airflow with matching units.
- Review volume and hourly air exchange.
Frequently asked questions
Which airflow units can I use?
The converter supports m3/min, m3/h, and cfm and normalizes them before dividing by room volume.
Is ventilation equal to air quality?
No, air changes are a capacity estimate, not measurement of CO2, VOCs, pollen, or filtration performance.
Limits and interpretation
- Equivalent air changes assume complete and uniform mixing; dead zones, short-circuit flow, and furniture can reduce effective ventilation.
- Real delivery also depends on duct pressure, filter resistance, fan curves, and occupancy, so use it as a design estimate.