intro question to tracking ROI and ROR

[yanicehand]

i have lurked in the forums for the past two months while slowly making SNGs on party my main focus. I'd attribute Harrington's new book as well as these forums for vastly improving my game as of late. To make a long story short, I've been crudely tracking all my information on pen and paper, and now that I have about 150 SNGs under my belt, I was wondering the correct way to calculate ROI. I assume this is a relatively simple procedure, but how does everyone calculate/track this information? I was also curious as to figuring out ROR (which I believe can facilitate my decision as to how much bankroll is required to safely play a level?) I apologize for the ignorance of this post, but I figured this was the best place to get answers.

Thanks.