Student level work will use that much RAM? And does windows use up 3-4gb RAM even though I am not doing anything to it? I'm new to all this VM stuff and am not really sure.
I'm a computer science student and I run about 3-4 VMs simultaneously, usually.
For you, I'm not sure, but assuming that you assign 4GB of RAM to Windows (I find that it runs best with at least this amount, for a 64-bit build of Windows), and that Autodesk Inventor eats up even more, then yes, you're better off with 16GB.
You can never have too much RAM