# Circumference of a Semicircle

## Method #1 – Circumference from the Radius

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

π is approximately equal to 3.1415926535

### Example

A semicircle has a radius of 10

Circumference = (π x 10) + (2 x 10) = (3.14159 x 10) + (2 x 10) = 314.159 + 20 = 334.159

## Method #2 – Circumference from the Diameter

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

π is approximately equal to 3.1415926535

Circumference = (π x Diameter ÷ 2) + Diameter

##### Example

A semicircle has a diameter of 20

Circumference = (π x 20 ÷ 2) + 20

Circumference = (3.14159 x 10) + 20

Circumference = 314.159 + 20

Circumference = 334.159

## Method #3 – Circumference from the Area

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

π is approximately equal to 3.1415926535

Step 1: Find the radius from the area

Radius = √(2 x Area ÷ π)

Step 2: Find the circumference from the radius

##### Example

A semicircle has an area of 300

Radius = √(2 x 300 x π)

Radius = √(2 x 300 x 3.14159)