Sequence search
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Fun fact about π
How it works
How do you find a number inside π?
π is an irrational number: its decimal digits never end and never repeat periodically. Pi Finder goes through those digits looking for the first time the sequence you typed appears, and shows you its position, counting from the first digit after “3.”.
A database that grows as you use it
The page already includes the first 100,000 digits of π. As soon as you arrive, it loads the first million from this same site in the background, without slowing the page down. If your sequence does not show up, the deep search keeps expanding the database: to 5,000,000 and up to 10,000,000 digits.
Those digits were calculated with the Chudnovsky brothers’ algorithm (1988), the same kind of formula used for record-breaking calculations, and verified with two independent implementations. Each file is checked when it is downloaded and stays saved only in your browser, so future searches are instant.
How likely is it to find your number?
The more digits a sequence has, the more digits of π it takes to find it. This table estimates the probability that any given sequence appears in each range:
| Digits in your number | 100,000 | 1 million | 5 million | 10 million |
|---|---|---|---|---|
| 4 | > 99% | > 99% | > 99% | > 99% |
| 5 | 63% | > 99% | > 99% | > 99% |
| 6 (short date) | 9.5% | 63% | 99% | > 99% |
| 7 | 0.99% | 9.5% | 39% | 63% |
| 8 (full date) | 0.1% | 1% | 4.9% | 9.5% |
| 9 | 0.01% | 0.1% | 0.5% | 1% |
That is why a 6-digit date (such as MMDDYY) almost always shows up in the deep search, while an 8-digit date (MMDDYYYY) only shows up sometimes.
Frequently asked questions
What people ask us most
Why can’t you search infinitely many digits?
π has infinitely many digits, but any search works with a finite amount: they have to be calculated first. World records are set with specialized hardware over weeks or months. Pi Finder searches the first 10 million digits, precomputed and verified.
Is my birthday in π?
It depends on the format. As a 6-digit date (MMDDYY or DDMMYY) it is almost certain to be found within the first 10 million digits. As an 8-digit date (MMDDYYYY) the probability drops to about 10%; if it does not show up, try the 6-digit version.
Does every number appear somewhere in π?
Nobody knows. π is believed to be a “normal” number, meaning that every sequence of digits appears at some point and with the expected frequency, but this has not been proven yet.
What does the position mean?
It is where the first digit of your sequence sits, counting decimal digits: position 1 is the first decimal digit (the 1 in 3.14…). Position 0 is the integer “3”.
Is my number sent to any server?
No. The search runs entirely in your browser. The digit files that get downloaded are the same for every visitor and do not depend on your number. Your history and the digits are stored only on your device, and your number is not added to the page address unless you choose to share the link.
How much data does the deep search use?
Each million digits takes up 0.5 MB. Reaching 10 million means downloading about 5 MB in total, just once: after that they stay saved in your browser. Only what is needed to find your number is downloaded.