Pi Day 2024: What is pi? Activities, facts, and why we celebrate the digits today

International Pi Day is celebrated on March 14
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Tom Herbert14 March 2024

Maths fans rejoice, because one of the most exciting days in the number-crunching calendar is here.

March 14 is recognised annually as Pi Day, a celebration of the mathematical constant pi.

Observed in some parts of the world by consuming and throwing pies, National Pi Day has also been recognised by the US House of Representatives.

Here's everything you need to know about Pi Day.

What is International Pi Day?

International Pi Day is a chance for maths enthusiasts to celebrate the number pi - represented by its first three digits of 3.14.

Many use the day to discuss the number, recite its infinite digits and eat plenty of pie.

It is celebrated on the same day every year - March 14, which this week is on a Thursday.

Why is it celebrated on March 14?

Happy International Pi Day

Granted, this method only works for those countries that write dates in the month then day format, but written down March 14 looks like 3.14, which are the first three digits of pi.

Since the exact value of pi can never be calculated, the numbers 3.14 are used to approximate the value of pi in other calculations.

However in a lot of countries, including the UK, the format is the other way round - meaning the day is written first, followed by the month.

Since this would make Pi Day look like 14.3, in many places outside America it doesn't make sense, which has led to calls for the celebration to be either scrapped or celebrated on Pi Approximation Day on July 22 (22/7 in the day first format) or Tau Day on June 28 (6/28 in the month first format).

What is pi?

Pi is a mathematical constant, which is a number that has a special meaning for calculations.

The constant Pi means the ratio of the length of a circle's circumference to its diameter - a value which is always the same for any circle.

The first 50 digits of pi are 3.14159265358979323846264338327950288419716939937510.

Pi Day activities

If you're a teacher and want to get some of the youngsters involved in Pi Day, or you just want to celebrate it with your own children, there are a number of fun activities you do on Thursday.

You could try and memorise as many digits of pi as you possibly can - a fun but nonetheless tricky activity to try.

Otherwise, you could make a paper chain with different colours representing digits and decimal points.

Or you could even bake a pie, and try to fit in as many digits on the pastry lid as you possibly can.

Pi facts

  • It is thought the concept of pi was first discovered around 4,000 years ago.
  • We can never find the true meaning of pi because it is what is known as an "irrational number".
  • Welsh mathematician William Jones was the first person to use the symbol we now use for pi more than 250 years ago.
  • The Guinness World Record for most decimal places memorised is held by Rajveer Meena, who took 10 hours to recall 70,000 places blindfolded in March 2015.
  • British mathematician William Shanks became famous for manually calculating pi to 607 places in the 19th century. However it later emerged the 527th number was wrong, making the rest of his calculations wrong by default.

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