Pi Day — Berry pie with pi symbol cutout and dough digits around the edge

Pi Day

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Published September 21, 2026

Pi Day is the annual math holiday celebrated on March 14, whose numeric date (3/14) matches the first three digits of π (about 3.14159). What began as a small 1988 procession at the San Francisco Exploratorium grew into an internet tradition of pie puns, memorized-digit bragging contests, and Einstein-themed math jokes each year.

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Overview

Pi Day mixes genuine math appreciation with dumb wordplay. The joke rides on the phonetic overlap between π and pie, so posts, classroom events, and memes on March 14 pivot on pie-eating gags, pie-throwing bits, and photos of circular baked goods labeled with strings of digits1. Reciting memorized digits of π grew into its own bragging tradition, with self-identified math geeks posting how far they can go from memory4.

The holiday also folds in Albert Einstein, whose birthday falls on March 14, so celebrations often stretch into a general science theme rather than just π itself1. Google marks the date with themed Pi Day Doodles5, and MIT times its regular admissions decisions to Pi Day, turning the holiday into a running joke among high schoolers waiting on results3. Some math purists also nod to July 22 (22/7), the older fractional approximation, but the 3/14 version is the one that stuck online4.

Origin & Background

Platform
San Francisco Exploratorium (offline origin) / math forums and blogs (online spread)
Creator
Larry Shaw
Date
1988

The first Pi Day happened on March 14, 1988, organized by American physicist Larry Shaw at the San Francisco Exploratorium1. Staff scientists and visitors marched in a circular procession around one of the museum's rotundas and then ate fruit pies afterward, locking in the food pun that still defines the holiday3. Because March 14 also happens to be Einstein's birthday, Shaw's team let the day expand into a broader celebration of math and science, not just π on its own1.

How It Spread

The Exploratorium's ritual stayed a local museum event for years before math teachers, university clubs, and early web forums picked it up through the late 1990s and 2000s. By the mid-2000s, Urban Dictionary entries were already describing Pi Day as "a holiday celebrated by math geeks everywhere," with commenters posting long recited strings like "3.141 592 6535 8979 323 84..." as a form of nerd flex4.

In March 2009, the U.S. House of Representatives passed H.RES.224, formally recognizing March 14 as National Pi Day and urging schools to use the date to draw students into mathematics2. The vote gave the holiday a legitimacy boost that news outlets and educators leaned on in later coverage3. Google added Pi Day to its Doodle rotation, illustrating the date with pie-shaped and equation-heavy artwork5.

The 2016 edition drew extra attention because 3/14/16 rounds π to five digits (3.1416), pushing the hashtag and pie photos across Twitter, Facebook, and school accounts more visibly than usual years3. Since then, Pi Day is still the reliable annual excuse for math memes, pie photos, and Einstein posts every March 14.

Timeline

1988-03-14

Larry Shaw runs the first Pi Day at the San Francisco Exploratorium, complete with a circular march and fruit pies.

2009-03-11

The U.S. House of Representatives passes H.RES.224, officially recognizing March 14 as National Pi Day.

2010-03-14

Google publishes a dedicated Pi Day Doodle, giving the holiday major mainstream online visibility.

2016-03-14

The 'five-digit' Pi Day (3/14/16 ≈ 3.1416) trends heavily on Twitter, Facebook, and school pages.

Frequently Asked Questions