July 22 is Pi Approximation Day. Also known as Casual Pi Day, the day is dedicated to the mathematical constant pi (π). Celebrate pi (π) by eating pie, throwing pies, and discussing the significance of the number π. Pi denotes the relationship between a circle’s circumference and its diameter and is denoted by the fraction 22/7 which calculates approximately to 3.14

Pi can be expressed as the fraction 22/7, which is an approximation of its actual value (hence the word “approximation” in the day’s title). Pi Approximation Day is particularly celebrated in countries that write their dates in the date/month format, where today’s date would be written as 22 July or 22/7.

How to Observe

Here are a few ideas on how to celebrate the day:

  • Eat some pie—stop at a restaurant or bakery, or make your own.
  • Eat some pizza.
  • Memorize as many digits of π as you can. You can start by learning the first 10,000 digits. Quiz yourself or challenge your friends to see who can learn the most.
  • Do some math problems using pi.

Pi Approximation Day Dates:

Year Weekday Date Name
2020 Wed 22 Jul Pi Approximation Day
2021 Thu 22 Jul Pi Approximation Day
2022 Fri 22 Jul Pi Approximation Day
2023 Sat 22 Jul Pi Approximation Day
2024 Mon 22 Jul Pi Approximation Day
2025 Tue 22 Jul Pi Approximation Day