How do I calculate how much I can sue for in a civil suit?

I was in an online classroom discussion board. An individual threatened me with physical violence, then posted that I was a registered sex offender when I am not. They then filed a false police report claiming that I threatened them by leaving threatening emails and voicemails and that I got their phone number off the internet, when they gave it to me on the post board. I am claiming stress and mental anguish, libel, slander, filing a false report, threats and defamation of character. How much can I calculate monetarily in a civil suit?