What size return air vent should be used for a 2.5 ton ac unit?

For a 2.5-ton AC unit, a typical return air vent size would be around 20x20 inches or 14x24 inches, depending on the specific airflow requirements and duct design of the system. It's important to calculate the total airflow needs, which is generally around 400 CFM (cubic feet per minute) per ton, to ensure adequate ventilation. Consulting with an HVAC professional can help determine the exact size needed for optimal performance.