What is Pi Day?

Pi Day has been celebrated each year on March 14 (3/14) as a fun salute to pi = 3.14…  This year, Pi Day will have special significance because 3/14/15 at 9:26:53 a.m. and p.m. will represent the first 10 digits of pi. Plus, March 14 happens to be Albert Einstein’s birthday. Cool!


What is Pi?

Pi is is the ratio between the circumference (distance around a circle), and the diameter (the distance across the circle). It written as p in Greek alphabet, which is the symbol π. Pi is an infinite decimal with a value 3.14159265358979323846…

Want more details? SciShow has an explanation of pi useful for older students.

Activities for Pi Day:



1. Baking

It has become somewhat of a tradition to bake a pie to share for Pi Day with a π symbol on it. Another option would be to make π pancakes. Simply make a π shape out of pancake batter and let it brown, then add more pancake batter over the top to fill in the pancake. Or you can use a dark pancake batter, such buckwheat, to create the π symbol and a lighter batter for the background.

2. Toothpick Toss

One way to calculate pi involves comparing the circumference of a circle to the diameter. Another way is to count how many toothpicks (or other similar objects) fall in a certain way when thrown at a series of parallel lines.


  • Toothpicks (matchsticks also work) – at least 100
  • Cardboard or poster board surface to draw lines on
  • Ruler
  • Marker (such as Sharpie)
  • Calculator (optional)

Draw several parallel lines on the cardboard or poster board with the distance between each line exactly equal to the twice the length of a toothpick. Randomly toss toothpicks onto the lined surface, keeping track of the total number of toothpicks tossed. When you are done, count each toothpick that has landed crossing a line in any way. 

Divide the total number of toothpicks tossed by the number of toothpicks that crossed the lines. See how close to pi your estimate is.

For more details and slightly different methods, check Estimating pi by dropping sticks (with a simulation to try) at SciFriday. Exploratorium also has a discussion the toothpick toss and other Pi Day Activities.

3. Read a Pi Day Book

Sir Cumference and the Dragon of Pi (A Math Adventure)
by Cindy Neuschwander and illustrated by Wayne Geehan

Meet the regulars in King Arthur’s court, such as Sir Cumference, his wife Lady Di of Ameter, their son Radius, and the carpenter, Geo of Metry. When Sir Cumference turns into a dragon, can his family and friends use math to save him? Although it looks a bit like a picture book, the concepts are actually for middle grades.

For more book suggestions, check the list of Math Books for Pi Day and Every Day at Science Books for Kids.


Want more? There’s a plethora of links to all things pi at Joy of Pi.


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