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.
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
and a is the arc angle.
How to calculate the are of an arc?
The area of an arc can be thought of as a portion of an area of a full circle. In that respect, it’s easy to just use the formula for the area of a circle, and then multiplying by the ratio of the angle to 360 degrees.