Calculate shaded area and boundary length for circles, sectors, annuli, and rectangles with holes or cutouts using length and area units.

Shaded Area Calculator

Outer Shape Dimensions

Unshaded Shape Dimensions

Shaded Area = Outer Area – Unshaded Area

Shaded Area Formula

The following two example problems outline the steps and information needed to calculate the Shaded Area.

SA = L² - pi*(L / 2)²
  • Where SA is the Shaded Area contained by the square and the circle
  • L is the diameter or length of a square or circle 

To calculate the shaded area, square the diameter or length, then subtract the result of pi times the length over 2 squared.

How to Calculate Shaded Area?

The following example problems outline how to calculate Shaded Area.

Example Problem #1:

  1. First, determine the diameter or length of a square or circle.
    • The diameter or length of a square or circle is given as: 25.
  2. Finally, calculate the Shaded Area using the equation above: 

SA = L^2 - pi*(L/2)^2

The values provided above are inserted into the equation below and computed.

SA = 25^2 - pi*(25/2)^2 = 134.12


Example Problem #2: 

For this problem, the variables required are provided below:

diameter or length of a square or circle = 30

${V2} = ${number 4}

Test your knowledge using the equation and check your answer with the calculator..

SA = L^2 - pi*(L/2)^2 = ?