How is the value of pi obtained and why does pi not have units?

Question

How is the value of pi obtained and why does pi not have units?

Answer 1

There are many series that converge to pi. For example,

4 - 4/3 +4/5 -4/7 +4/9 -4/11 +4/13 - ...

Answer 2

pi is the ratio of a circle's circumference to its diameter.  

Circumference has the units length, diameter also has units of length.  

Since pi is a ratio of two lengths, it itself has no dimension.

Answer 3

pi is a mathematical constant so it does not have uniits

Answer 4

Pi is a ratio.  This is why it doesn't have units.  The value is calulated from dividing the circumference of a circle by its diameter.  Pi is an irrational number and is also transcendental.