"Pi is all things infinite, or inscrutable, or unpredictable, or full of endless wonder." -Alex Bellos

We have calculated Pi to 13 trillion digits.

The circumference of a circle is the distance around the outside.

To calculate the circumference of a circle, first you use the diameter. You take the diameter, the distance across the circle, and multiply it by Pi! Then you have the circumference of the circle.

Archimedes was the first person to calculate Pi.

The radius is the distance from the center of the circle to the edge of the circle.

To find the area of a circle, you use the radius instead of the diameter. You multiply the radius by itself, or square it, and then multiply it by Pi. This gives you the area of the circle.

Albert Einstein was born on Pi Day, in 1879.

A sector is a part of a circle defined by two radii.

To find the area of a sector, first you have to find the area. Then, you use this proportion.

The practice of memorizing Pi is called piphilology.

Pi is an endless, infinite, irrational number, and is used in many ways.