[paul.fr]

why do we need to know the value of Pi to so many decimal places? how does this help, and what with?

[neilep]

I love pie !

Isn't it because ?......we simply must know !!.......it's a case of the ' It's because it's there ' syndrome type thing !!

[another_someone]

In theory, Pi is used all over the place, and improving its accuracy might give more accurate results; but in practice, we would not be able to verify those results with similarly accurate measurements.

I suspect most of the issue about calculating Pi to large numbers of places is to develop and prove the software concepts (and the maths) that allow you to make these calculations, rather than being too concerned about what the answer actually is.

[ludviglizana]

A detailed knowledge of π can for example be used in bench mark tests of computers and software