I need to know and apparently I'm mathing it wrong.

there's no official conversion, it's whatever users will sell/buy it for. IMO the price of CSC in sP is a little high right now, I think it should be 10MsP for 100CSC and 50MsP for 500CSC

What about USD? Isn't it 1:1?

Edit: Woops! Sorry that posted twice.

aha sorry I missed that part of your original question. The USD to CSC ratio is official, it has no agio (if you buy larger amounts, the agio goes negative) and only goes one way from USD to CSC.

One USD equals 100CSC.