National Pi Day

Pi Day is an annual American holiday dedicated to the number pi. This famous mathematical constant has fascinated mathematicians and scientists for centuries. Its relative, Euler’s number, is another important irrational value. Both represent infinite non repeating decimals. Pi Day is observed on March 14.

History

Pi Day was created by physicist Larry Shaw, who noticed that the approximate value of pi, 3.14, matches the date format 3/14. This made March 14 a fitting day to celebrate the mathematical constant.

Historians believe that ancient civilizations, including Babylon, understood the concept of pi. Some theories suggest it was used during large scale construction projects, possibly even in calculations for structures mentioned in ancient texts. There is also speculation that pi may have been applied in the construction of the Temple of King Solomon.

The symbol π was introduced by Welsh mathematician William Jones in 1706 in his work A New Introduction to Mathematics. The notation was later popularized by the mathematician Leonhard Euler.

Interesting Facts

• Mathematically, pi is defined as the ratio of a circle’s circumference to its diameter.
• A common myth claims that Euler discovered pi, but William Jones used the symbol earlier.
• Pi has appeared in literature and film. For example, in Carl Sagan’s novel Contact, characters explore the number’s mysteries in their search for extraterrestrial communication.

How to Take Part

Work on math problems involving pi or explore interesting facts about the constant. Celebrate in a culinary way by baking a round cake or pie decorated with the pi symbol.

Share information about the holiday on social media to help others learn about Pi Day.

When is National Pi Day in 2026?

National Pi Day is observed on March 14 each year.

Observations