Pi Day 2027 falls on Sunday, March 14, 2027. It is the one day of the year when mathematicians, teachers, bakers and pizza lovers all celebrate the same thing: the number pi (π), 3.14159…, the ratio of a circle’s circumference to its diameter. The date is the joke — written the American way, March 14 becomes 3/14, the first three digits of pi. This guide explains what pi actually is, how a San Francisco museum physicist turned it into a holiday in 1988, why March 14 is also Albert Einstein’s birthday, and how to celebrate Pi Day 2027 — including the $3.14 deals to watch for.
Pi Day 2027 at a Glance
| Detail | Pi Day 2027 |
|---|---|
| Date | Sunday, March 14, 2027 |
| Written as | 3/14 — the first three digits of pi (3.14) |
| What it celebrates | The mathematical constant pi (π), about 3.14159 |
| Founded | 1988, by physicist Larry Shaw at the San Francisco Exploratorium |
| Official status | Recognized by the U.S. House of Representatives in 2009; UNESCO’s International Day of Mathematics since 2019 |
| Also on March 14 | Albert Einstein was born (1879); Stephen Hawking died (2018) |
| Public holiday? | No — it is an unofficial observance |
| Next occurrences | 2028: Tuesday, March 14; 2029: Wednesday, March 14; 2030: Thursday, March 14 |
Why March 14? The Date Is the Punchline
Pi Day exists because of a calendar coincidence that only works in the American date format. In the United States, dates are written month first, so March 14 becomes 3/14 — and 3.14 are the first three digits of pi. In countries that write the date day-first, 14/3 does not read as 3.14, which is one reason the holiday is most popular in the United States.
The celebration even has its own moment: 1:59 p.m. on March 14 gives you 3.14159, the first six digits of pi. The most devoted fans mark the “Pi Moment” at 1:59:26 p.m. And 2015 was “Super Pi Day” — 3/14/15, the first five digits — with 9:26:53 a.m. giving the first ten digits, 3.141592653.
What Is Pi, in Plain English?
Pi (π) is the ratio of any circle’s circumference to its diameter. Measure any circle — a coin, a pizza, a planet’s orbit — divide the distance around it by the distance across it, and you always get the same number: about 3.14159. It does not matter how big or small the circle is.
Two things make pi special. First, it is irrational: its decimal digits go on forever without ever repeating, so no fraction and no finite decimal can ever equal it exactly. Second, it shows up everywhere — in engineering, architecture, navigation, and even in the way ripples spread across water and planets orbit the sun. That is why a single number earned its own day.
A Short History of Pi Itself
Pi Day is only 39 years old, but the number it celebrates has been chased for nearly 4,000 years.
- Around 1900–1600 BC: Babylonian mathematicians estimated pi at about 3.125. Egyptian scribes, in the Rhind Papyrus (around 1650 BC), used about 3.1605.
- Around 250 BC: Archimedes of Syracuse made the first rigorous calculation, using a 96-sided polygon to show pi lies between 3 1/7 (about 3.1428) and 3 10/71 (about 3.1408). Pi is sometimes still called Archimedes’ constant.
- 1706: Welsh mathematician William Jones first used the Greek letter π for the number.
- From 1737: Leonhard Euler popularized the symbol, and it stuck.
- 1768: Swiss mathematician Johann Heinrich Lambert proved pi is irrational — its digits never end and never repeat.
- 2022: Pi was calculated to 100 trillion digits. By 2024, the record had passed 105 trillion digits, computed with the y-cruncher program.
Nobody needs a trillion digits to bake a pie, of course. But the record-chasing is part of the fun: pi recitation contests, where people memorize as many digits as possible, are a Pi Day tradition.
How Pi Day Began: Larry Shaw and the Exploratorium, 1988
Pi Day was founded in 1988 by Larry Shaw, a physicist at the Exploratorium, the hands-on science museum in San Francisco. During a staff retreat, Shaw connected pi’s first digits to the date March 14 and organized the first celebration: staff and visitors marched around one of the museum’s circular spaces — because pi is about circles — and then ate fruit pies.
The celebration went public the following year, and the Exploratorium still marks it with a parade at 1:59 p.m. every March 14. From one museum, the idea spread to classrooms, libraries and bakeries across the country.
Official recognition followed. On March 12, 2009, the U.S. House of Representatives passed a non-binding resolution (H.Res. 224) recognizing March 14 as National Pi Day. In November 2019, UNESCO’s 40th General Conference designated Pi Day as the International Day of Mathematics, giving the March 14 celebration a global, official name.
March 14’s Other Famous Connection: Einstein and Hawking
Pi Day shares its date with two of the most famous names in science. Albert Einstein was born on March 14, 1879 — a coincidence math lovers never tire of pointing out. And Stephen Hawking died on March 14, 2018, Einstein’s 139th birthday. The triple convergence — pi, Einstein’s birth and Hawking’s death — is one reason March 14 feels like science’s unofficial holiday, and why many Pi Day celebrations double as a birthday party for Einstein.
How to Celebrate Pi Day 2027
Pi Day works for almost any age and any budget. Here are the ideas that actually get used, from classrooms to kitchens:
- Bake (or buy) a pie. The pun is the point. Apple, cherry, key lime, pizza pie — any pie counts. Decorate the crust with the π symbol or the digits 3.14159.
- Hold a pi recitation contest. See who can recite the most digits from memory. Most people manage 3.14159; the serious competitors go much further.
- Run 3.14 miles. “Pi runs” are a real thing — a 3.14-mile fun run, ideally ending at pie.
- Do a pi craft or experiment. Measure round objects at home — plates, lids, wheels — divide circumference by diameter, and watch every answer come out near 3.14.
- Teach it. Teachers use Pi Day for circle lessons, pi-themed worksheets, and pie-eating math games. It is one of the easiest math holidays to build a lesson around.
- Watch a math movie night. Films like Pi (1998) or Hidden Figures pair well with the day — or keep it lighter with a pie-and-trivia night.
- Share a pi pun. “Come to the math side — we have pi.” “Irrational, but I love you.” “You want a piece of me?” Pi Day puns are, by tradition, terrible — and mandatory.
If you are celebrating with kids, keep it hands-on: baking, measuring circles, and a memorization game beat a lecture every time. If you are celebrating at work, a pie in the break room at 1:59 p.m. is the classic move.
Pi Day Deals: What to Expect in 2027
Pi Day has become a genuine deals day for pizza and pie, with many chains offering items for $3.14. No 2027 offers have been announced yet — this article was checked on November 8, 2026, and chains typically announce their Pi Day deals in the week before March 14 — but last year’s pattern shows what to expect:
- Blaze Pizza (2026): buy one 11-inch pizza, get a second for $3.14 at participating locations.
- 7-Eleven (2026): a whole one-topping pizza for $3.14 for rewards members, plus cinnamon sugar fried pies for 31.4 cents.
- Burger King (2026): a free Hershey’s Sundae Pie or Cinnamon Apple Pie with any purchase of $3.14 or more through the app.
- Marco’s Pizza (2026): a medium one-topping pizza for $3.14 with a large or extra-large pizza, using code PIDAY.
- Papa John’s (2026): a second large or XL pizza for $3.14 for rewards members.
- BJ’s Brewhouse (2026): a regular Pizookie for $3.14 with a shareable or large pizza purchase.
- Papa Murphy’s (2026): 31.4% off regular-priced items with a promo code.
Expect the 2027 versions of these offers to appear in early March 2027. Most require a rewards app or membership, and nearly all are limited to participating locations on March 14 only — check the chain’s own site or app before you go.
Pi Day vs. National Pie Day — Don’t Mix Them Up
Pi Day (March 14) is often confused with National Pie Day, which falls on January 23 — a completely separate day celebrating the food, not the number. The two days share a pun and a dessert, but their dates, origins and purposes are different. If you already celebrated National Pie Day 2027 in January, Pi Day is your second helping.
Related reading on this site: National Pie Day 2027, National Puzzle Day 2027, National Trivia Day 2027, St Patrick’s Day 2027, Easter 2027.
Pi Day Jokes and Puns
- What do you get when you take the sun and divide its circumference by its diameter? Pi in the sky.
- Why should you never talk to pi? Because he’ll go on forever.
- What is a mathematician’s favorite dessert? Pi, à la mode.
- Why did pi get its driver’s license revoked? Because it didn’t know when to stop.
- Come to the math side. We have pi.
Frequently Asked Questions
Q: When is Pi Day 2027? A: Pi Day 2027 is on Sunday, March 14, 2027. It is always March 14, every year.
Q: Why is Pi Day on March 14? A: Because in the American month/day format, March 14 is written 3/14 — the first three digits of pi (3.14).
Q: Who invented Pi Day? A: Physicist Larry Shaw founded it in 1988 at the San Francisco Exploratorium, where staff marched around a circular space and ate fruit pies.
Q: Is Pi Day a public holiday? A: No. It is an unofficial observance — no one gets the day off — though it was recognized by the U.S. House of Representatives in 2009 and named UNESCO’s International Day of Mathematics in 2019.
Q: What is pi, exactly? A: Pi (π) is the ratio of a circle’s circumference to its diameter, about 3.14159. It is irrational, so its digits never end and never repeat.
Q: Is Pi Day the same as National Pie Day? A: No. National Pie Day is January 23 and celebrates the food. Pi Day is March 14 and celebrates the mathematical constant — though eating pie is encouraged on both.
Q: What is Pi Approximation Day? A: July 22 (22/7), because the fraction 22/7 is a close approximation of pi. It is a smaller, alternate celebration.
Q: What are the best Pi Day deals? A: Chains typically offer $3.14 pizzas and pies — Blaze Pizza, 7-Eleven, Marco’s and Papa John’s did so in 2026. No 2027 deals had been announced when this article was checked on November 8, 2026; expect announcements in early March 2027.
Sources
- Pi Day — Wikipedia: https://en.wikipedia.org/wiki/Pi_Day
- 15 Fun & Creative Ways to Celebrate Pi Day — Why Pi: https://www.whypi.org/what-are-some-fun-and-creative-ways-to-celebrate-pi-day-on-march-14th/
- Pi Day 2026 & 2027: Exact Dates, Days & Celebration Ideas — Calendarena: https://calendarena.com/usa/pi-day/
- Pi Day Deals 2026 — Parade: https://parade.com/food/pi-day-deals-2026
- Pi Day Facts, History & Records — Practice Pi: https://www.practicepi.com/pi-facts