Every year on March 14, students, teachers and math enthusiasts around the world celebrate Pi Day, honoring one of mathematics’ most recognizable constants: pi, the number used to calculate the circumference of a circle.

Pi, written as 3.14 in its simplest form, represents the ratio of a circle’s circumference to its diameter. Because the date matches the first three digits of the number, 3/14, March 14 has become the unofficial holiday for mathematics and science.

Pi continues infinitely without repeating, making it one of the most fascinating numbers in mathematics. While many people round it to 3.14, mathematicians and computer scientists have calculated trillions of digits beyond the decimal point.

Schools across the country often mark Pi Day with classroom activities and pie-themed events that connect math with food. Students commonly compete to recite as many digits of pi as possible, while teachers use the day to make math more engaging.

The day also carries significance in science and engineering because pi plays a critical role in calculations involving circles, waves, motion and space exploration. Engineers, physicists and astronomers regularly rely on pi in everything from bridge construction to satellite trajectories.

Pi Day also shares a birthday with physicist Albert Einstein, who was born March 14, 1879, adding another scientific connection to the famous day.

The modern Pi Day celebration began in 1988 at Exploratorium in San Francisco, where physicist Larry Shaw organized one of the first public events on the mathematical constant. In 2009, the United States Congress officially recognized March 14 as National Pi Day.

For many educators, Pi Day offers more than a lesson in numbers. It gives students a chance to see how mathematics connects to everyday life.

Though the celebration often includes slices of pie and playful competitions, the day also highlights the lasting importance of mathematics in modern life, all built around a number that never truly ends.