Calculate the area of any semi-circle. Enter the radius and total degrees of the rotation (arc) of the semi-circle to calculate the area. The degree of rotation is the angle between the end line/points.

## Semi Circle Area Formula

The formula the calculator uses is as follows:

Area = PI (3.141) * r ^2 * a/360

• Where r is the radius
• a is the arc angle also known as the central angle. (For a semi-circle this is always 180 degrees)

## Area of a semi circle definition

The area of a semi-circle is defined as the total area occupied by half of the area of the circle enclosed by the given radius.

## How to calculate the area of a semi circle?

How to calculate the area of a semi circle

1. Measure the Angle

The first step is to ensure that the area you are looking to calculate is in fact a semi-circle. If you do find this to be the case, the angle in the formula above will be 180 degrees. If this is not the case, then you must find the angle by measuring it. For this example, we will assume it is in fact a semi-circle, so the angle is 180.

The next step is to measure or calculate the radius. For this example, we are going to assume the diameter of the semi-circle is given at 2 meters (m). To find the radius we must divide the diameter by 2. This yields a result of 1 meter for the radius.

3. Calculate the Area

The final step is the plug all of the information into the formula or simply use the calculator. Using the formula we find the area of this semi-circle is 1.570 meters squared.

4. Analyze the results

Analyze the results and determine if the answer makes logical sense. This step is key in determining the accuracy of your calculations.

## FAQ

What is the area of a semi circle?

The area of a semi-circle is defined as the total area occupied by half of the area of the circle enclosed by the given radius.