Pi, which is denoted by the Greek letter (), is the most famous ratio in mathematics, and is one of the most ancient numbers known to humanity. PI is approximately 3.14, by definition, the number of times that a circle's diameter will fit around the circle. PI goes on forever, and can't be calculated to perfect precision.
On our site and in all of our calculators, 3.14159 is the value we use, unless otherwise specified. (You can also calculate it yourself using our PI Calculator. Dividing the PI(e) has always been a problem but sometimes multiplying with it is also. You can do either here; PI power is also available.) The only exception is the expatiated calculation below. (I didn't have much to do last night and TV was terrible - the only thing on was the 8,534,565th repeat of Hawaii 50 (divided by PI), so I calculated PI to 10,000 places on my 1959, still working, easy on the eye yellow, NASA issue, Pickett slide rule. I was going to try for a million but the slide was a little dirty and I felt accuracy MIGHT be compromised... We certainly don't want to compromise PI!) The value 3.14159 was defined in 1998 by the Alabama legislature as the official state value for PI. (I'll bet you didn't know that you needed a state value for PI. Of course, they also said that PI are round and cornbread are squared... They would have been better served to say that PI was to personal taste.) This infinite calculation phenomena is known as the decimal expansion of PI. No apparent pattern emerges in the extreme succession of digits; a predestined yet unfathomable code. They do not repeat periodically, but seemingly do pop up repeating a few sequences by blind chance, (lacking any perceivable order, rule, reason, or design). In 1991, the Chudnovsky brothers in New York, using their computer, m zero (in my opinion, named for the important work it did), calculated PI to two billion two hundred sixty million three hundred twenty one thousand three hundred sixty three digits (2,260,321,363). They halted the program that summer. Was it important? Some thought it was; others feel it was a waste of time, effort and energy. PI has had various names (some of them not fit for family viewing) through the ages, and all of them are either words or abstract symbols (something like the symbol for the entertainer (?) formerly known as Prince...), since PI is a number that can't be shown completely and exactly in any finite form of reasonable representation. PI is a true transcendental number, one that can't be expressed in any finite series of either arithmetical or algebraic operations. PI departs from all rational methods to locate it. It is virtually indescribable and can't be found. Ferdinand Lindemann, a German mathematician, proved the transcendence of PI in 1882, not that I felt he needed to prove it. PI possibly first entered human consciousness in Egypt. The earliest known reference to PI occurs in a Middle Kingdom papyrus scroll (produced on a very old MAC, or a bad Apple), written around 1650 BC by a scribe named Ahmes. He began the scroll with the words, "The Entrance Into the Knowledge of All Existing Things" and remarks in passing that he composed the scroll "in likeness to writings made of old." Towards the end of the scroll, which is composed of various mathematical problems and their solutions, the area of a circle is found using a rough sort of PI. The next indication of the value of PI occurs in the Bible. It is found in 1 Kings chapter 7 verse 23, where using the Authorized Version, it is written "... and he made a molten sea, ten cubits from one brim to the other: it was round about ... and a line of thirty cubits did compass it round about." Thus their value of PI was approximately 3. (Works for me... I'm a believer!) Even though this is not as accurate as values obtained by the Egyptians, Babylonians and Indians, it was good enough for measurements needed at that time, give or take a cubit. Around 250 BC, Archimedes of Syracuse found that PI is somewhere about 3.14 (in fractions, Greeks did not yet have decimals in a math system). Rumor has it, that is also when swearing started. As time went on, other people were able come up with better approximations (as opposed to calculations) for PI. About 150 AD, Ptolemy of Alexandria (Egypt) gave its value as 377/120 and in about 500 AD the Chinese Tsu Ch'ung-Chi produced the value as 355/113. These are correct to 3 and 6 decimal places respectively. In fact, they are accurate enough that MOST 8 place calculators of modern era use one or the other as a basis for PI. (We use the latter.) Knowledge of PI then bogged down until the 17th century, shortly before Mr. Gates introduced double precision numeric variables in MBASIC (well it SEEMS like that long ago...). PI was then called the Ludolphian number, after Ludolph van Ceulen, a German mathematician. It is also rumored that his number is used in the price formula of BMWs. The first person to use the Greek letter for the number was William Jones (try keeping up with him...), an English mathematician, who coined it in 1706. Physicists have noted the ubiquity of PI in nature. PI is obvious in the disks of the moon and the sun. The double helix of DNA revolves around PI. PI hides in the rainbow (and in the refrigerator), and sits in the pupil of the eye, and when a raindrop falls into water PI emerges in the spreading rings. PI can be found in waves and ripples and spectra of all kinds, and therefore PI occurs in colors and music (and sometimes at your local ATM or local Girl Scout bake sales). PI has lately turned up in values known as superstrings. PI occurs naturally in tables of death, in what is known as a Gaussian distribution of deaths in a population; that is, when a person dies, the event "impacts" PI. It is one of the great mysteries in life how nature seems to know (of) mathematics; yet, for those of us that are believers, it is really no mystery at all. (Another great mystery of PI(e) is why you can always find apple and cherry but seldom egg custard.) Please see our Historical Computation Of PI Table.
(Source: The New Yorkermagazine, March 2, 1992, called "Profiles: The Mountains of PI")
), is the most famous ratio in mathematics, and is one of the most ancient numbers known to humanity. 
