To find the area of a semicircle, use the formula 1/2(pi x r^2). You need the value of "r," or radius of the circle, and pi.

**Determine the radius**Measure the distance from the center of the circle of which the semicircle is part to its edge. This is its radius.

**Find r2**Multiply the radius of the semicircle by itself.

**Multiply pi by r^2**Find the product of pi, which is rounded to 3.14, and the square of the radius.

**Determine the area**Using the formula for finding the area of a semicircle, divide the product of the squared radius and pi by 2. If the radius of the semicircle is 2 centimeters, then the area is 1/2(3.14 x 2 x 2), or 6.28 square centimeters.