Bandwidth needed for a forum site....

how much and how much $?

[CuriousWeb]

I am considering setting up a forum site for users of certain types of commercial software.

Depending on the success the number of users could range anywhere from 1000 up to 10s of 1000s.

I am unsure of what amount of bandwidth I would need to buy and how much I should be paying...

Any ideas, suggestions appreciated...

[Tapolyai]

What forum software are you thinking of?
Is there lot of graphics?
Are message threads come as a list (a la WebmasterWorld), or have to read one by one (threaded)?
How many of these users will be posting?

Here is a very very very simplistic formula:

A..........1,000 Visitors Daily 
 B..............4 Threads read by single visitor 
 C.............20 Average message count in single thread 
 D..............1 Size of single message in KB 
 E..C x D......20 Single thread size in KB 
 F..B x E......80 Messages read by single visitor in KB 
 G..A x F..80,000 Total KB read daily by all visitors

This of course does not include over head, such as your menus, adds, banners, logos, graphics, etc. Add that to E and you can "guess" of your bandwidth needs. It's close enough for starting.

[CuriousWeb]

Tapolyai - Thanks for the reply.

I was thinking of using one of the free boards that are available and customizing slighty although I shouldn't think I'd need to do this much. There's another thread on here that I was reading giving a few suggestions. Graphics will be minimal so this shouldn't add too much. Message threads will be lists like this place but in total probably only around 50% or less of the number of forums.
It's hard to say how many of the users will actually be posting. I'd appreciate any feedback from forum owners as to the ratios of users to posters as it seems to be that lots of lurking goes on as well..
My main concern is not to go with too little bandwidth as if I exceed it I know I will get stung, but on the other side of the coin too much is just a waste...

thanks again