π is known to 10 trillion digits. 39 is enough to calculate the size of the universe to the radius of 1 atom.
The most accurate calculation of pi before the advent of the computer was by D F Ferguson, who calculated pi to 620 digits in 1945.
William Shanks had calculated pi to 707 digits in 1874, but only 527 digits were correct.
D F Ferguson calculated pi to 710 digits in 1947 with a desk calculator.
Takahashi Kanada calculated pi to 206,158,430,000 digits in 1999 with a Hitachi SR8000.
Japanese systems engineer Shigeru Kondo and Alexander Yee, a US computer science student, set about calculating the constant to more decimal places than anyone else using only a home computer.
It took 90 days to calculate pi at Kondo's home using a desktop computer with 20 external hard disks. It ran on the operating system Windows Server 2008R2 and used powerful Intel microprocessors. Verification took 64 hours.
In 2011 Kondo used Yee's Y-cruncher program on a supercomputer to calculate pi to 10 trillion digits.
By the time you read this, someone will probably have calculated even more digits.