I'm looking to get a site going, and part of these plans are that I get X amount of bandwidth for X amount of dollars. If I go over in bandwidth, I presume downtime is a penalty, and downtime is not okay.

If I am running an information site (no sales), any tips on how to calculate bandwidth so I don't get stuck with not enough, but likewise am not buying too big of a plan?

How do I calculate things?

Here is a site that helps explain the basics of bandwidth including a simple way to calculate the bandwidth.

http://www.findmyhosting.com/bandwidth.htm

It is a very handy site that I have been using ofr a bit ot help figure out if I was going over my bandidth because my site will just shutdown as well, which is very bad of course.

Hope this helps a bit.

That looks like a pretty good site.

Most companies will allow you to upgrade your package to the next package size at any time. So if you purchase too small of a plan and hit downtime or whatever penalty, then you can go in and buy more bandwidth allowance.