# Area of a semi circle calculator

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 degrees of rotation is the angle between end line/points.

## Semi Circle Area Formula

Technically, a semi circle always has a degrees of 180, hence the term semi, which means half of a circle. I suspect you may be visiting this page to calculate the area of an arc, or piece of a circle, because semi circle can sometimes be considered ambiguous.

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)

## How to calculate the area of a semi circle

The follow example is a step by step guide on how to calculate the area of a semi circle.

1. 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 a in the formula above will be 180 degrees. If this is not the case, then you must find the angle by measuring it or calculator it. For this example we will assume it is in fact a semi circle so the angle is 180.
2. 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. The final step is the plug all of the information into the formula above, 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 and determine if the answer makes logical since. This step is key in determining the accuracy of your calculations.