Enter the width, height, radius, angle of bend, and quantity into the calculator to determine the duct bend area.

Duct Bend Area Formula

The following formula is used to calculate a duct bend area.

A = (W + H) * 2 * [(R+W/2)*3.14159*(a/180)] * Q
  • Where A is the area
  • W is the width
  • H is the height
  • R is the radius of the bend
  • a is the angle of the elbow

This formula is used specifically for a duct elbow bend.

What is a duct elbow?


A duct elbow is a bend in an air duct that changes the direction of the duct and airflow. Calculating the area of the bend is important for understanding how air will flow through the bend.

How to calculate duct bend area?

Example Problem:

The following example outlines how to calculate a duct bend area.

First, determine the width of the duct. In this example, the width is 10 inches.

Next, determine the height. In this case, the height is 12 inches.

Next, determine the bend radius. The bend radius for this duct is measured to be 10 inches.

Next, determine the angle of the bent. This is measured to be 45 degrees.

Next, determine the quantity. This is 2 in this case.

Finally, calculate the duct bend area using the formula above:

A = (W + H) * 2 * [(R+W/2)*3.14159*(a/180)] * Q

A = (10 + 12) * 2 * [(10+10/2)*3.14159*(45/180)] * 2

A = 1036.72 in^2