CFM Calculator – Calculate Required Airflow
Use this free CFM calculator to determine the required airflow in cubic feet per minute for room ventilation, exhaust fans, engine airflow, and compressed air systems.
Imperial
Metric
CFM = (Floor Area × Ceiling Height × ACH) ÷ 60
CFM = Area × Velocity
CFM = (Engine Displacement × RPM × VE) ÷ 3456
CFM = (Receiver Volume × (End Pressure – Start Pressure)) ÷ (Fill Time × 14.7)
CFM Calculator FAQs
What is CFM?
CFM stands for Cubic Feet per Minute, which measures the volume of air flowing through a space in one minute. It’s a standard measurement used in HVAC, ventilation, and airflow calculations.
What is ACH?
ACH stands for Air Changes per Hour, which indicates how many times the air in a room is completely replaced with fresh air in one hour. Higher ACH values are needed for rooms with more pollutants or moisture.
What is a good CFM for a bathroom exhaust fan?
For bathrooms, a minimum of 1 CFM per square foot is recommended, with at least 50 CFM for standard bathrooms. Larger bathrooms may require 80-110 CFM.
How do you calculate CFM for room ventilation?
For room ventilation, CFM = (Floor Area × Ceiling Height × ACH) ÷ 60. Floor area can be calculated as length × width, and ACH depends on the room type and usage.
What is Volumetric Efficiency in engine airflow?
Volumetric Efficiency (VE) is a measure of how effectively an engine can move air in and out of the cylinders. Naturally aspirated engines typically have 80-90% VE, while forced induction engines can exceed 100%.