March 14th is Pi Day!

Happy 3.14159265359 Day! That’s right, the 14 March is the annual worldwide celebration of Pi. Pi is represented by the Greek symbol π. The number Pi (π) is a mathematical constant whose value is the ratio of any circle circumference (C) to its diameter (d) and is approximately equal to a rational expression of 3.14159. However, the Pi number is irrational meaning that it is a non-repeating, non-terminating decimal and continues to an infinite number of places without any pattern. Pi has been calculated by computers to 2.7 trillion digits so far!!


Pi Day is a celebration of mathematics and is a great opportunity for teachers to help their students discover and explore Pi. Read on below for some ideas!

Ideas for Key Stage 1 and 2

Make a Paper Chain: Use a different color of paper to represent each digit. Have each class work on a section and see how long the chain is by the end of the day.

Bring in Cookies to Measure: Bake cookies of different sizes. Have the pupils measure the width of each cookie. Once they’ve measured their cookie, they can eat is as a treat.

Make Pi Plates: Bring in paper plates and glue the pi symbol to the plate. Then write the digits of pie around the edge of the plate– using a different color for each digit.

Throw a Pizza Party: Talk about pi and celebrate by eating different circle-shaped foods like pizza, cookies, and pie! (This is great for Key Stage 3 & 4 too!)

Ideas for Key Stage 3 and 4

Buffon’s Needle: Use a toothpick and have parallel lines drawn that are the length of the toothpick apart. Drop the toothpick from about a foot above the paper record whether it lands touches a line or not. The ratio of hits to total is 2/pi if you drop the toothpick enough. Explore why.

Pi Graph: Use a large piece of graph paper and label the x or horizontal axis as “Diameter” and the Y-axis or vertical axis as “Circumference” . Take several size cylindrical objects (cans, coins etc.) and mark the diameter of the object on the x axis. You then roll the object up carefully and mark its location after it has completed one revolution. Each object will create one point and if you connect the points the slope of the line will be Pi!

Pi Competition: Have a competition to see which pupils can memorize the most digits of pi. This website can help pupils prepare.