Determine proper ventilation for any room. Enter dimensions, pick the room type, and get the CFM you need. Learn more
Air flow calculator
Determine proper ventilation for any room. Enter dimensions, pick the room type, and get the CFM you need.
You handle the airflow. Workiz handles the rest — scheduling, dispatching, invoicing, and payments, all in one place.
How to calculate CFM for a room
CFM (cubic feet per minute) is the standard measure of air volume moving through a space. This calculator gives you a fast, accurate result based on room dimensions and air change requirements.
How to calculate CFM:
- Determine room volume — Length x Width x Height.
- Select ACH — Different rooms need different air changes per hour.
- Apply the formula — Room volume multiplied by ACH, divided by 60, gives you the CFM.
Once you know the CFM, use the duct size calculator to pick the right duct for that airflow. If you need to size the whole system first, start with the HVAC load calculator.
Frequently asked questions
What is CFM and why does it matter?
CFM stands for cubic feet per minute. It measures the volume of air moving through a space. Getting the CFM right ensures a room stays comfortable, meets building ventilation codes, and maintains the right temperature.
What is the difference between ACH and CFM?
ACH is how many times the air in a room is fully replaced in one hour. CFM is the volume of air moving per minute. To convert: multiply the room volume by ACH and divide by 60. This calculator handles that math automatically.
What are the signs of poor airflow?
Hot spots, stuffy air, and condensation on windows are clear signs. If your space feels uncomfortable despite the HVAC running, the vents may not be delivering enough CFM for the square footage.
How much CFM do kitchens and bathrooms need?
These rooms require higher airflow to remove moisture and odors. Bathrooms typically need 50-100 CFM. Kitchens often need 100-300 CFM depending on the ventilation setup. Getting these numbers right is vital for preventing mold and maintaining air quality.
Does ceiling height affect CFM requirements?
Yes. CFM is based on room volume, not just floor area. A room with 10-foot ceilings has 25% more volume than the same room with 8-foot ceilings, and needs proportionally more airflow.