Skip to main content

Pi Day – a Holiday for Math Geeks

A part-time college economics & finance instructor who began his career in banking, Chuck frequently writes on money & economics online.

A Holiday Celebrating an Equation

March 14th is Pi Day in the United States. If you have never heard of this holiday, don’t worry, as this is a special holiday observed mostly by math geeks and a few math teachers. Since Pi is usually written as 3.14 and the shorthand in the U.S. for dates is month/day/year or month/day, March 14th becomes 3/14/year making March 14th the day to celebrate Pi – at least many math geeks see it this way.

If you think back to grade school or high school when you first encountered the section in math that dealt with the calculation of area – square feet, square miles, etc., you many recall hearing about Pi. For rectangular shapes the calculation was easy, simply multiply the length times the width to get the area. But, when it came to circles the math became more complicated.


Pi - Key Part in Calculating Area of a Circle

The formula for calculating the area of a circle is Pi times the radius squared or Area = Pi x R2 where the radius is the distance between the center of the circle to its outer edge (or half the diameter which is defined as a straight line that passes through the center of the circle from one edge to the other edge).

Pi itself is the ratio of the circumference to the radius which, for all circles, works out to be approximately 22/7. When the fraction 22/7 is converted to a decimal by dividing 22 by 7 it comes to 3.141592653589… with the decimal places continuing on forever without ever reaching zero (computers have calculated it out to over a trillion decimal places and still haven’t found the end).

Historically, it has only been carried out a few decimal places (3.14 now days and 3.1416 when I was in school) on the theory that the tiny increase in accuracy of measurement was not worth the extra multiplication involved.

Frankly, I have never encountered a situation in my life where I have had to know the area of a circle and I am sure that this is true for most people. For the few who need this, a simple 3.14 times the radius squared is probably sufficient.

In addition to the date in the American format being 3/14, March 14th is also the birth date of Albert Einstein (born March 14, 1879) the brilliant mathematician (of E=MC² fame) who could explain the mysteries of the universe but could never remember where he left his glasses. It is easy to see how the number combination of the date plus the fact that one of the greatest mathematicians of all time was born on the same date would be a reason for geeks to celebrate.

Pi Explained on Pi Day

March 14th is π Day in America Because of How We Write Dates

The March 14th Pi Day date is observed mostly in America, because our short hand for dates is to use numbers in the form of month/day/year.

However in many other countries the dates are displayed as day/month/year, so the March 14th date is of little significance in these countries.

This difference in the date format between Americans and people in other countries sometimes causes other problems. Thus a European acquaintance may text their American friend suggesting they meet at a certain ski resort in Switzerland on 2/3 (March 3rd) and the American shows up on February 3rd and wonders where their friend is.

Other Pi Days - In Case You Miss the American March 14th Day

If you forget to celebrate the March 14th Pi Day, there are other days that have some connection to Pi and these are dates that are also celebrated as Pi Day or, more accurately, Pi Approximation Day, as the numbers frequently used for Pi are approximations given that the decimals go on for infinity. Other dates on which Pi Day is celebrated in other parts of the world (as well as by some math geeks in the U.S.) are:

April 26th (or April 25 during Leap Years) which is the day on which the distance of the Earth's orbit divided by the time it has traveled is equal to Pi.

July 22nd - using the European day/month notation this day is written as 22 / 7 and 22 divided by 7 gives the 3.14 decimal equivalent of Pi.

November 10th (or November 9th during Leap Years) which is the 314th day of the year.

December 21st at 1:13 p.m. which is the 355th day of the year and the significance of 1:13 p.m. is the fact that the Pi originally calculated in ancient times by the Chinese (ironically about the same time as it was calculated in the West) came out to 355/113. I don't know if they start the party at 1:13 or just celebrate it during the minute the clock is on 1:13.

There are probably other days that also qualify as Pi Day, but, as yet, I haven't found them. However, it is a good thing that this holiday can be celebrated on a number of different days scattered throughout the year.

To date this holiday is not well advertised which makes it easy to forget, especially for math geeks who are so totally focused on their work that they tend to forget things like parties and holidays.

Scroll to Continue

Given that approximately half the world either forgets or would forget their wedding anniversary unless their wife reminds them, it is easy to see how it would be easy to forget the unpublicized anniversary of an obscure math formula.

How to Celebrate Pi Day

So, how does one celebrate Pi Day?

Like any holiday, this is up to the individual, however, certain customs are beginning to emerge, with most of them having a math focus.

Like other holidays, there are merchants ready to supply Pi themed decorations for the celebration including Pi T-Shirts, coffee mugs, and jewelry., which claims to be the official website of the March 14th Pi Day has a shop on the site that includes these and other momentous for Pi Day.

Pies of any kind are great food for this day as their name not only sounds the same, but most pies are round thereby keeping with the circle focus of the holiday.

Math games, math trivia, math problems, math jokes, etc., especially ones involving Pi in some manner, are popular activities. The WikiHow site lists a whole page of activities and ideas for activities.

There are also Pi Carols which can be sung. Since this is a relatively new holiday, even though it celebrates an ancient mathematical formula, there is plenty of room for improvisation as well as a growing number of websites popping up with suggestions. However, like any other holiday, π Day is a chance for people sharing a common culture (love of math in this case) to get together and have fun.

Pi Day will pass unnoticed by most of us and, unlike other holidays, such as Christmas or Valentine’s Day, it will have very little or no impact on retail sales figures.

However, for those who live and breath numbers it is their day to celebrate their life's passion. If you know a math geek, you can wish them well on their special day by sending them a Pi Day e Card. Free Pi Day e Cards are available from, and probably other online greeting card sites as well.

© 2007 Chuck Nugent


Chinemere onuekwusi on November 05, 2010:

Hi Chuck and thanks for this expose, a walk down history, and a very important history at that. Now going by your assertion, it also means that the Italian mathematician pythagoras could have been born also in march looking at his theorem on solving trigonometric problems. Since the triangle has 3 sides and the third month of the year is march, then pythagoras going by your calculation was born in march. Thanks for this wonderful formula for calculating birth dates of famous mathematicians of the ages (lol), atleast I can now calculate other dates of some of my favorite scientist going by their various discoveries.

Denise Handlon from North Carolina on August 05, 2010:

Thanks Chuck, :)

Chuck Nugent (author) from Tucson, Arizona on August 04, 2010:

Denise Handlon - glad you enjoyed my Hub and thanks for the comments and link.

For those who would like to check out your Hub "13 Reasons to Hail the #13" here is a link to it ( 13 Reasons to Hail the #13 ) which I looked up and enjoyed reading.

Denise Handlon from North Carolina on August 03, 2010:

Hey Chuck, great hub. Thoroughly enjoyed all of the trivia info you provided. My dad would have loved it-he was a math genius. I connected with your hub after linking it with mine: 13 Reasons to Hail the #13. (hope you don't mind). Thanks for providing a good read--I'm off now for a piece of pi(e).

Lovina57 from Singapore on February 24, 2010:

awesome stuff! math geek celebration here we come!

Ada on February 01, 2010:


Pi day is just around the corner. Celebrate! If Daniel Tammet can memorize 22,000+ digits, you should be able to get 100? Practice up at, I'll record you best score.


AJHargrove from USA on May 27, 2009:

Wow. Pi day got a brief mention in past math classes but... Like I said - wow. I never knew there was such a culture behind it.

thecounterpunch on May 05, 2007:

OK next year I will celebrate PI day :)

Related Articles