## Method #1 – Radius from the Area

### Formula – How to calculate the radius of a semicircle from the area

π is approximately equal to 3.1415926535

Radius = √(2 x Area ÷ π)

##### Example

A semicircle has an area of 300

Radius = √(2 x 300 ÷ π)

Radius = √(2 x 300 ÷ 3.14159)

## Method #2 – Radius from the Circumference

### Formula – How to calculate the radius of a semicircle from the circumference

π is approximately equal to 3.1415926535

##### Example

A semicircle has a circumference of 35

Radius = 35 ÷ π = 35 ÷ 3.14159 = 11.14086