On March 14, written 3/14 in the U.S. date format, math lovers around the world celebrate Pi Day. Pi, written with the Greek letter π, is the ratio of a circle's circumference to its diameter, about 3.14159. Its digits go on forever without repeating. Pi Day is a favorite in schools and science museums, with pie-eating, digit-memorizing contests and circle-measuring experiments, and it happens to be Albert Einstein's birthday too.
History of Pi Day
People have known about pi for thousands of years. Ancient Babylonians and Egyptians used approximations close to 3.1, and the Greek mathematician Archimedes, around 250 BC, calculated that pi lies between 3 1/7 and 3 10/71 using polygons. The symbol π was popularized in the 1700s by mathematicians William Jones and Leonhard Euler.
Pi Day was founded in 1988 by physicist Larry Shaw at the Exploratorium science museum in San Francisco, where staff marched around a circular space and ate fruit pies. The celebration spread to schools and universities.
In 2009, the U.S. House of Representatives passed a resolution recognizing March 14 as National Pi Day. In 2019, UNESCO proclaimed March 14 the International Day of Mathematics. With modern computers, pi has been calculated to trillions of digits, though only a few dozen are needed for most science and engineering.
Why Pi Day Matters
Pi appears everywhere in math, science and engineering, from calculating the area of a pizza to modeling waves and planetary orbits.
Pi Day makes math fun and approachable, encouraging students who might not think of themselves as 'math people'.
How to Celebrate Pi Day
- Eat pie: celebrate with a fruit pie, pizza pie or pot pie.
- Measure circles: measure circumference and diameter of household objects and divide.
- Memorize digits: see how many digits of pi you can learn.
- Celebrate at 1:59: some people mark 3/14 at 1:59 for 3.14159.
- Learn about Einstein: March 14 is his birthday.
Celebrating at Work, School and Home
At work, Pi Day is an easy reason for a pie social; engineering and data teams may enjoy a pi-digit quiz or a 'most creative circle' contest. In classrooms, students can measure circular objects with string and rulers, divide circumference by diameter, and discover pi for themselves, or hold a digit-memorizing contest. Art classes can make 'pi skylines' using the digits as bar heights. At home, families can bake a pie together, measuring the pan's circumference and diameter first, or order pizza and calculate the area of each slice. Celebrate at 1:59 p.m. for extra fun.
Fun Facts About Pi Day
- Archimedes estimated pi around 250 BC.
- Pi Day was founded by Larry Shaw in 1988.
- UNESCO named March 14 the International Day of Mathematics in 2019.
Pi Day FAQs
When is Pi Day?
Pi Day is March 14 (3/14).
What is pi?
The ratio of a circle's circumference to its diameter, about 3.14159.
Who started Pi Day?
Physicist Larry Shaw at the San Francisco Exploratorium in 1988.
Is there an International Day of Mathematics?
Yes. UNESCO declared March 14 the International Day of Mathematics in 2019.