We love celebrating special days during each month of the year. It’s even better to celebrate by sharing pie!

Pi Day is an annual celebration of the mathematical constant π (pi). Pi Day is observed on March 14 (3/14 in the month/day format) since 3, 1, and 4 are the first three significant digits of π. In 2009, the United States House of Representatives supported the designation of Pi Day. UNESCO’s 40th General Conference decided Pi Day as the International Day of Mathematics in November 2019.

Pi Day is when mathematicians and math lovers around the world celebrate pi, often approximated to 3.14, which is the ratio of a circle’s circumference to its diameter.

The circle is often the first shape many learn in childhood, and can be observed in nature in pinecones, apples, oranges, the cornea in our eyes…the circle is everywhere!

The first calculation of pi was done by Archimedes of Syracuse (287-212), an ancient Greek mathematician and astronomer. He calculated the area of a circle with the use of the Pythagorean Theorem.

Pi has been used by different cultures throughout history. The ancient Babylonians and Egyptians used approximations for pi when calculating the area of a circle. Zu Chongzhi (429–501), a Chinese mathematician, created his own ratio that approximated pi in much the same way Archimedes did. Georges-Louis Leclerc (1707-1788), a French mathematician, showed that Pi could be calculated with probability.

Since its discovery, pi has been used every day. Engineering, construction, GPS, simulation, radio, TV, telephones, power generation, motors…all of this is possible thanks to the magic of pi! Some historians even debate whether pi was used when the ancient Pyramids of Giza were constructed because the structures are nearly perfect geometrically.