Skip to content
Calculator Tools
HVAC Calculators

CFM Calculator

Airflow in CFM for a room from air changes per hour, and the fan size it implies.

Enter values

Results update as you type.

Result

Airflow required

176.6 CFM

In m³/hour
300
In litres per second
83.33
Room volume
50 m³
Air changes per hour
6
Fan size to fit
200 mm fan

About the CFM Calculator

Airflow in CFM for a room from air changes per hour, and the fan size it implies.

Also known as: air changes calculator, ventilation cfm, extractor fan size, airflow calculator.

How to use this calculator

  1. Enter room length, room width, ceiling height, room type and the other fields.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

CFM = room volume × ACH × 0.5886

Worked example

Using the values pre-filled in the calculator above:

  • Room length = 5 m
  • Room width = 4 m
  • Ceiling height = 2.5 m
  • Room type: Living room (6 ACH)

the calculator returns:

  • Airflow required: 176.6 CFM
  • In m³/hour: 300
  • In litres per second: 83.33
  • Room volume: 50 m³