Geometry

##### Related Lessons

- 3 4 5 Triangle
- 30 60 90 Triangle
- 45 45 90 Triangle
- 5 12 13 Triangle
- Arc Length Calculator
- Area of a Circle Calculator
- Area of a Hexagon
- Area of a Kite
- Area of a Parallelogram
- Area of a Pentagon
- Area of a Rectangle
- Area of a Rhombus
- Area of a Sector
- Area of a Semicircle
- Area of a Square
- Area of a Trapezoid
- Area of a Triangle
- Center of Mass Calculator
- Circumference Calculator
- Distance Formula
- Distance Formula Calculator
- Geometry Calculators
- How to Find the Height of a Triangle
- Isosceles Triangle Theorem
- Perimeter of a Circle
- Perimeter of a Pentagon
- Perimeter of a Rectangle
- Perimeter of a Rhombus
- Perimeter of a Semicircle
- Perimeter of a Square
- Perimeter of a Trapezoid
- Perimeter of a Triangle
- Properties of a Parallelogram
- Pythagorean Theorem Calculator
- Side Angle Side Theorem
- Side Splitter Theorem
- Similar Triangles
- Special Right Triangles
- Surface Area of a Cone
- Surface Area of a Cube
- Surface Area of a Cylinder
- Surface Area of a Hemisphere
- Surface Area of a Pyramid
- Surface Area of a Sphere
- Surface Area of a Triangular Prism
- Triangle Inequality Theorem
- Types of Triangles
- Vertical Angles
- Volume of a Cone
- Volume of a Cube
- Volume of a Hexagonal Prism
- Volume of a Pyramid
- Volume of a Sphere
- Volume of Hemisphere
- Volume of Parallelepiped

Tutors/teachers:

Nikkolas

Tutor and Aerospace Engineer

# Perimeter of a Circle

## How to Find the Perimeter of a Circle

The perimeter of a circle is called the circumference. The formula for perimeter of a circle is the circumference formula. It is given as:**C = 2πr**

or:**C = πd**

Where *C* is the circumference, *r* is the radius of the circle, and *d* is the diameter of the circle. Here is an example of using this formula to find circumference of a circle with a radius of 3.

C = 2π(3) = 6π, circumference = 6π.

A circle with labeled dimensions.

### Example Problems:

**Problem 1:**

Find the circumference of a circle with a radius of 10.

Solution:

Let’s plug the radius into the circumference formula.

C = 2πr = 2π(10) = 20π**The circumference is 20π.**

**Problem 2:**

Find the circumference of a circle with a diameter of 10.

Solution:

Let’s plug the diameter into the circumference formula.

C = πd = π(10) = 10π**The perimeter is 10π.**

**Problem 3:**

Compare the perimeter of a circle with a diameter of 7 to a square with a side length of 7. The formula for perimeter of a square is P = 4s.

Solution:

Let’s plug the circle’s diameter into the circumference formula. Solving for circumference gives us the perimeter.

C = πd = π(7) = 7π.

Now let’s do the same for the square.

C = 4s = 4(7) = 28**The circle’s perimeter is 7π (≈22) and the square’s perimeter is 28.**

Result :

Worksheet 1

Download.pdf

Cheat sheet

Download.pdf