# Return Air Duct Size Calculator

## About Return Air Duct Size Calculator (Formula)

The Return Air Duct Size Calculator is a tool used to determine the appropriate size of the return air duct for an air conditioning system. The return air duct plays a crucial role in providing a path for air to flow back to the air conditioner for cooling or heating.

The formula used to calculate the return air duct size depends on the shape of the duct. Here, we’ll focus on the formula for a rectangular air duct:

Drect = √(AS * 144)

In this formula:

• Drect represents the return air duct size for a rectangular duct.
• AS denotes the air conditioner size in tons, which refers to the cooling or heating capacity of the air conditioner.

To calculate the return air duct size, the air conditioner size (in tons) is multiplied by 144, which converts the value to square inches. The square root of this product is then taken to obtain the return air duct size in square inches.

Determining the appropriate size for the return air duct is essential to ensure proper airflow and efficient operation of the air conditioning system. An undersized duct can restrict airflow, leading to reduced performance and potential strain on the equipment. Conversely, an oversized duct may result in excessive air pressure and inefficient operation.

Using the Return Air Duct Size Calculator simplifies the process of selecting an appropriate duct size based on the air conditioner’s capacity. By inputting the air conditioner size, the calculator quickly provides the recommended size for the return air duct in square inches.

Keep in mind that this calculator assumes a rectangular duct shape. If you have a circular duct or other variations, alternative formulas and considerations may be necessary. Consulting HVAC professionals or reference materials specific to your system can help ensure accurate duct sizing for optimal performance.