Calculating the frequency of an open end pipe?

[Qaiphyx]

How can this be done. I know it has to do with the length, but what about the width? Does that have any bearing?

 

[olivermsun]

The pipe diameter has a slight influence because the antinode doesn't form exactly at the open end of the pipe. The effect is very small if the pipe is much longer than it is wide (but you will probably want to account for it if you're tuning a pipe organ!). A quick search on "pipe end correction" gives tons of references.