MTMasterTool

CFM Calculator

Calculate ventilation airflow from room volume and desired air changes.

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What this tool does

Calculate ventilation airflow from room volume and desired air changes. ACH is not the same as heating/cooling airflow or an outdoor-air code requirement.

How to use the CFM Calculator

  1. Enter or select room length in ft.
  2. Enter or select room width in ft.
  3. Enter or select room height in ft.
  4. Enter or select air changes per hour.
  5. Read the calculated result; change any measurement to compare alternatives.

Formula

CFM=length×width×height×ACH/60
length
Room length (ft, before metric conversion)
width
Room width (ft, before metric conversion)
height
Room height (ft, before metric conversion)
ach
Air changes per hour

ACH is not the same as heating/cooling airflow or an outdoor-air code requirement.

Worked example

For cfm calculator, the following measurements illustrate the exact method: Room length: 20; Room width: 15; Room height: 8; Air changes per hour: 6.

Inputs

  • Room length20 ft
  • Room width15 ft
  • Room height8 ft
  • Air changes per hour6

Result

  • Required airflow (CFM)240

Results explained

Required airflow (CFM)
Required airflow (CFM) from the formula above. ACH is not the same as heating/cooling airflow or an outdoor-air code requirement.

Frequently asked questions

CFM=length×width×height×ACH/60

ACH is not the same as heating/cooling airflow or an outdoor-air code requirement.

No. Electrical and HVAC results are estimates. Installation must comply with local codes and be checked by a qualified licensed professional.

Nameplate values, conductor temperature, power factor, efficiency, weather and actual installation conditions may differ from your entered assumptions.

Confirm units, manufacturer data and the formula's assumptions, then verify sizing with the equipment instructions and applicable local standards.