Pi Day is a fun math-themed day celebrated every year on March 14 (3/14) because the date matches the first three digits of the mathematical constant pi, approximately 3.14.

What is Pi Day?

Pi Day is an annual celebration of the number π (pi), the ratio of a circle’s circumference to its diameter, about 3.14159. The date March 14 was chosen since written as 3/14 it lines up with the first three digits of pi.

Why pi matters

Pi shows up anywhere circles, spheres, or waves appear in math, science, and engineering. It is used to calculate areas and volumes of circular or spherical objects, from tiny molecules to planets and spacecraft trajectories.

How Pi Day started

Pi Day as a named celebration began in 1988 at the Exploratorium, a science museum in San Francisco, where staff marked the day with a circular parade and eating pie. The U.S. House of Representatives later officially recognized March 14 as National Pi Day in 2009.

How people celebrate

Common traditions include:

  • Eating or baking pies (because “pi” sounds like “pie” and pies are round).
  • Pi recitation contests, where people compete to remember as many digits of pi as possible.
  • Math games, classroom activities, and special lessons about circles and pi.
  • Events at museums, schools, and universities, sometimes including parades or pie-throwing.

Fun extra facts

March 14 is also Albert Einstein’s birthday, which gives the day extra science cred. Some years are considered extra special, like 2015, when the date 3/14/15 matched pi to more digits (3.1415).

Information gathered from public forums or data available on the internet and portrayed here.