HVAC CFM CALCULATOR

Calculate airflow in cubic feet per minute

Estimate system airflow from cooling capacity, or room airflow from volume and air changes per hour.

AIRFLOW BASIS

Choose what you know

System airflow and room air-change airflow answer different questions. Select the method that matches your job.

ESTIMATED AIRFLOW
1,200 CFM

3 tons × 400 CFM per ton

Next stepSize the duct pathUse this airflow in the duct-size calculator →

Airflow targets depend on equipment data, sensible heat ratio, humidity control, filtration, external static pressure, ventilation standard, and balancing. Verify the design target before changing blower settings.

FORMULAS AND LIMITS

Three calculations, with the basis kept visible

Capacity method

CFM equals cooling tons multiplied by design CFM per ton. Four hundred is a common starting point, but the correct target comes from the equipment and design conditions.

Room-volume method

CFM equals room volume multiplied by air changes per hour, divided by 60. This is a ventilation or circulation estimate—not a cooling-load calculation.

Duct measurement

CFM equals duct free area multiplied by average air velocity. A technician should use a traverse or another approved test method rather than one spot reading.