Pi Day
March 14 — 3 / 14 — 3.14
Countdown to Pi Day
π Today's Pi Digit
Day β of the year β Digit #β of Ο is
Ο Facts
Infinite & Irrational
Pi is an irrational number β its decimal representation never ends and never falls into a permanent repeating pattern. It has been computed to over 100 trillion digits.
Ancient Origins
The ancient Babylonians approximated Ο as 3.125, while the Egyptians used 3.1605. Archimedes of Syracuse (287β212 BC) was the first to rigorously approximate Ο between 310β71 and 31β7.
Circle Constant
Pi (Ο) is the ratio of a circle's circumference to its diameter. No matter the size of the circle, this ratio is always the same: 3.14159β¦
The Symbol
The Greek letter Ο was first used by Welsh mathematician William Jones in 1706. It was later popularised by the great Leonhard Euler in 1737.
Memory Champion
The world record for memorising digits of Ο is held by Rajveer Meena (India), who recited 70,000 decimal places in 2015 β taking nearly 10 hours!
Hidden Everywhere
Pi appears in many formulas across physics, engineering, and probability β from Heisenberg's uncertainty principle to the normal distribution (bell curve) and Einstein's field equations.
Famous Ο Formulas
Often called the most beautiful equation in mathematics.
An infinite series that converges (slowly) to Ο/4.
Sum of reciprocals of perfect squares equals ΟΒ²/6.
The fundamental formula relating Ο to the area of a circle.
Pi appears unexpectedly in probability and statistics.
An infinite product representation discovered in 1656.
Ο Approximations Through History
| Approximation | Value | Error | Origin |
|---|---|---|---|
| 3 | 3.000000 | 4.51% | Bible (1 Kings 7:23) |
| 25/8 | 3.125000 | 0.53% | Babylonia (~1900 BC) |
| 256/81 | 3.160494 | 0.60% | Egypt (~1650 BC) |
| 22/7 | 3.142857 | 0.04% | Archimedes (~250 BC) |
| 355/113 | 3.141593 | 0.000008% | Zu Chongzhi (~480 AD) |
| Ο | 3.141593β¦ | 0 | Exact (irrational) |
Ο in Different Number Bases
March 14 β A Day of Legends
Pi Day doesn't just celebrate mathematics β it shares its date with two of the greatest scientific minds in history.
Albert Einstein
β Born March 14, 1879 β Ulm, Germany
The father of the theory of relativity, Einstein revolutionised our understanding of space, time, and the universe. His equation E = mcΒ² became the most famous formula in all of physics. He was awarded the Nobel Prize in Physics in 1921.
"Pure mathematics is, in its way, the poetry of logical ideas."
Stephen Hawking
β Died March 14, 2018 β Cambridge, England
A visionary theoretical physicist and cosmologist, Hawking's work on black holes and the origins of the universe inspired millions. Despite being diagnosed with ALS at 21, he lived to 76 and authored the best-selling A Brief History of Time.
"However difficult life may seem, there is always something you can do and succeed at."
Pi Day History
First Pi Day Celebration
Physicist Larry Shaw organized the first Pi Day at the San Francisco Exploratorium, with staff and public marching around in circles and eating fruit pies.
Official U.S. Recognition
The U.S. House of Representatives passed a non-binding resolution (H.Res. 224) recognizing March 14 as National Pi Day.
Super Pi Day
March 14, 2015 (3/14/15) was called "Super Pi Day" because the date matched the first five digits of Ο (3.1415). At 9:26:53, the time aligned with 10 digits!
UNESCO International Day
UNESCO proclaimed March 14 as the International Day of Mathematics, officially making Pi Day a worldwide celebration.
100+ Trillion Digits
Pi has been computed to over 100 trillion decimal places, pushing the limits of modern computing and storage technology.
Ο Tools
π Find a Number in Ο
Search for any number sequence (birthday, lucky number, etc.) within the first 1,000 digits of Ο.
π Your Age in Ο Years
Enter your birth year to calculate your age in "Pi Years" (1 Pi Year = Ο regular years β 3.14159 years).
π§ Pi Memory Challenge
How many digits of Ο can you type from memory? Start typing after "3." and see how far you get!
The First 1,000 Digits of Ο
π Add Pi Day to Your Calendar
Never miss Pi Day again! Add it to your calendar now.