I need Internet usage calculator software

Usually we check Internet usage by analyzing the Web logs for the Web site.  Analog and AWStats are both free packages which will do this:
http://www.analog.cx/index.html
http://www.awstats.org/

Either one will read the Web logs of all of the major Web servers, and give you a report of how many kb have been downloaded from a Web site.  They will also give you basic reporting of how many people have been using the site, how many pages served, that sort of thing.

Do you want to know at the client-side as to how much data has been downloaded so far from the web-sites? Look at the size of your Temporary Internet files directory if you are using IE. But it won't give you the size of downloads done in other directories. If you have a download manager like Getright or Sun download manager then it should be easier, as long as their history is not cleared.

I am looking at software that will let me know how much internet bandwidth is being used for a particular website.

E.g. Assume I am using www.yahoo.com and hotmail.com for checking my emails and browsing. I wanted to know how much internet bandwith is being used for browsing yahoo.com and hotmail.com in separate report.

Is there any software that does this for me? I want to know how much MB I am using for yahoo.com and hot much of MB I am using hotmail.com

You can get a network monitor for your machine.  It will record the IP addresses your machine goes to, and their domain names (if you ask for the domain names to be looked up).

Reports from the network monitor will give you exact amounts of bandwidth for each IP address.  Statistics are gathered while the monitor is on.

You can also get some proxies (and firewalls) which will measure bandwidth, although if they give you reports by IP address, then they're likely to be more expensive.

Which OS are you on?  If you are on a Windows server machine, then the Microsoft Network Monitor comes with the operating system.  You can install it and turn it on for a day to see what your bandwidth is.

I am using Windows XP. How can I use the help of Microsoft Network Monitor to get the information?

What I understand from MS Network Monitor is it gives you "Total bytes sent" and "Total bytes received" . Does it also give information for every website?

The network monitor tells you the IP address to which and from which the total bytes are sent and received.  The IP address represents a Web site.

Can you help me out with MS Network monitor please? How do I use it to get information per IP address.

I have the Network connection icon on the task bar.