Air Changes Per Hour (ACH) Calculator
Result
Air Changes Per Hour (ACH) Calculator The Air Changes Per Hour (ACH) Calculator tells you how many times the entire volume of air in a room is replaced each hour by your ventilation. It uses the airflow rate and the room volume: ACH = (airflow in CFM × 60 — free online calculator.
Formula
- Air Changes Per Hour (ACH) Calculator calculates its result from Room Volume Cubic Feet, Airflow Cfm. It uses the formula ACH = (Airflow CFM × 60) ÷ Room Volume (cubic feet). Change any input to recalculate the result instantly.
- The main inputs are Room Volume Cubic Feet, Airflow Cfm. Enter them in the units and format shown in the calculator.
- Keep measurements and project assumptions consistent before comparing or combining values.
- Changing any input above recalculates the result with the same calculation engine used by this page.
Example: Air Changes Per Hour (ACH)
- Room Volume Cubic Feet: 2
- Airflow Cfm: 3
Using Room Volume Cubic Feet = 2, Airflow Cfm = 3, the calculated result is 90.
Sample result: Calculating…
Frequently asked questions
What does the Air Changes Per Hour (ACH) calculate?
Air Changes Per Hour (ACH) Calculator The Air Changes Per Hour (ACH) Calculator tells you how many times the entire volume of air in a room is replaced each hour by your ventilation. It uses the airflow rate and the room volume: ACH = (airflow in CFM × 60 — free online calculator.
Which values should I enter?
Enter Room Volume Cubic Feet, Airflow Cfm using the units and format shown beside each field.
What formula does this calculator use?
The calculator uses the following relationship: ACH = (Airflow CFM × 60) ÷ Room Volume (cubic feet).
Why might my result differ from another source?
Results can differ when another source uses different units, rounding rules, conventions or assumptions. Compare the inputs and definitions before comparing results.
Does the result update automatically?
Yes. Changing an input updates the result using the same calculation engine shown on this page.