How can I determine if my Web Application will handle anticipated traffic

Let's say I have a web site and I know how much traffic it currently attracts. Now I want to replace it with a new site and move from one hardwa开发者_StackOverflow社区re configuration to another.

How can I go about determining whether or not my application will support the anticipated load before hand?

---

This do the trick?

web capacity analyis tool http://support.microsoft.com/kb/231282