I wrote a compression ratio calculator tool in Excel so I could do some planning on my upcoming engine build.  There are tons of these tools out there on the web (that's how I tested this one) but the way I learn about topics like this is to follow along the calcs in excel.  And then, every once in a while, they are useful.  If anyone has Excel and wants this, send me a PM with your email.  Let me know what version of Excel you have - I have 2010, but I think I can downgrade it so it will work in 2007 or 2003.