Pi (π) Day

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Pi (π) Day March 14, 2020

Founded in 1988 at the Exploratorium, Pi (π) Day has become an international holiday, celebrated live and online all around the world. The numbers in the date (3/14) match the first three digits of the mathematical constant pi (π).

What is π, anyway? Divide any circle’s circumference by its diameter; the answer (whether for a pie plate or a planet) is always approximately 3.14, a number we represent with the Greek letter π. Keep calculating π’s digits with more and more accuracy—as mathematicians have been doing for 4,000 years—and you’ll discover they go on literally forever, with no pattern.

Celebrate Pi (π) Day online with the Exploratorium.

Learn More

Guide to Celebrating Pi (π) Day

Celebrate Pi (π) Day wherever you are.

Death of Archimedes
A Brief History of Pi (π)

Learn about the long and rich history of π.

A Slice of Pi (π) Day History

Learn about how π inspired a celebration and became a national holiday.

Activities

Science activity to demonstrate pi using circumference and string
Cutting Pi

String and scissors are all you need to find pi all around you.

Science activity to estimate pi with the random tossing of toothpicks
Pi Toss

Randomly toss some toothpicks, with pi as your reward.

Science activity using straight lines to learn about circles
Pi Graph

Use straight lines to learn about circles.

Exhibits

Pi Has Your Number
Pi Has Your Number

Use a touchscreen to search for any number hidden in the first 3 million digits of pi.

Pi Toss
Pi Toss

Toss some chips to estimate pi.

Pi Shrine
Pi Shrine

This circular piece of Exploratorium history has held pride of place in π Day festivities since 1988.