Pi Day 2026
Pi Day lands on March 14 because the date written 3/14 matches the start of π (about 3.14159…). What began as a playful Exploratorium staff tradition in San Francisco is now a worldwide excuse to talk about circles, irrational numbers, and — yes — actual pie.
About Pi Day
History & origins
Pi (π) is the ratio of a circle’s circumference to its diameter. In decimal form it begins 3.14159… and never ends or repeats. March 14 (month 3, day 14) lines up with those first three digits in the common U.S. date format, which is why the math holiday sits here. Albert Einstein was also born on March 14, 1879 — a coincidence many classrooms mention alongside the number.
Physicist Larry Shaw organized the first large-scale Pi Day celebration in 1988 at the Exploratorium science museum in San Francisco. After linking 3/14 to π at a staff retreat, he and colleagues marked the day with fruit pies and a circular parade. Shaw later installed a “Pi Shrine” plaque and kept leading museum festivities for years; the Exploratorium still hosts Pi Day events. Shaw died in 2017; the tradition continued without him.
The day spread through schools, science centers, and media. In 2009 the U.S. House of Representatives passed a non-binding resolution recognizing March 14 as National Pi Day. That is symbolic recognition, not a federal day off. A related date, Pi Approximation Day on July 22 (22/7), uses a common fraction approximation of π and is separate from March 14.
Why it matters
Pi Day makes an abstract constant feel approachable. It gives teachers a hook for geometry, measurement, and the idea of infinity, and it reminds everyone that math culture can be playful without being inaccurate.
How to celebrate
Bake or buy a pie and talk about why the date matches π. Measure circular objects and estimate circumference ÷ diameter. Hold a digit-memorization contest with short, safe limits. Visit a science museum program if one is local. Watch a short video about π’s history — from ancient estimates to modern computation — and keep the focus on curiosity, not perfection.
Facts
- π is the ratio of a circle’s circumference to its diameter; it begins 3.14159…
- Larry Shaw founded Pi Day celebrations at San Francisco’s Exploratorium in 1988
- March 14 is also Albert Einstein’s birthday (1879)
- The U.S. House recognized National Pi Day in a 2009 non-binding resolution
- July 22 (22/7) is sometimes called Pi Approximation Day and is a different observance
Upcoming dates
- Saturday, March 14, 2026
- Sunday, March 14, 2027
- Tuesday, March 14, 2028
- Wednesday, March 14, 2029
- Thursday, March 14, 2030
Frequently asked questions
When is Pi Day in 2026?
Pi Day in 2026 falls on Saturday, March 14, 2026.
Is today Pi Day?
No. Pi Day in 2026 falls on Saturday, March 14, 2026, not today.
What is Pi Day?
Pi Day is an annual celebration of the mathematical constant π on March 14, because 3/14 matches π’s leading digits. Many people also eat pie as a pun.
Who started Pi Day?
Larry Shaw, a physicist at the Exploratorium in San Francisco, organized the first major Pi Day celebration there in 1988.
How do you celebrate Pi Day?
Eat pie, explore circle math, memorize a few digits of π, or join a school or museum activity. Keep it educational and fun.
Is Pi Day an official holiday?
It is widely observed in STEM education and was recognized by a U.S. House resolution in 2009, but it is not a federal holiday or a day off work.
Share
Help others discover this day by sharing it.