What is the exact value of pi?

It is impossible to arrive at an exact value for pi because the digits that make up its decimal neither end nor repeat, according to Scientific American. It is therefore an irrational number, and the closest value that can be asserted is an approximation.

Shigeru Kondo, a Japanese systems engineer, and Alexander Yee, a U.S. computer scientist, collaborated to build a special computer that took over a year to calculate pi to the 10 trillionth digit. Extensive calculations of this sort are useful for testing the integrity of supercomputers and highly precise multiplication algorithms, but generally speaking, most scientific applications require no more than 40 decimal places.