RPI =
25% Your winning percentage
50% Your opponent's winning percentage (excluding games against you)
25% Your opponent's opponent's winning percentage (excluding games against your opponent)
Give you a base score.
Then you add to that bonus points for road victories against RPI top 25/50/75 teams. Bonus is higher for the higher categories (obviously). The bonus is calculated on the base score, not the bonus inflated scores.
Similarly, there is a penalty for home losses to really bad teams. I think it's sub-200 RPI, but not 100% sure on that.
HoustonFrog's quote of me from earlier was before I took the time to actually crunch the numbers. The DBU result isn't as big of a risk/reward discrepance as I originally thought. A win bumps us to the .5895 range. A loss down to the .583 range. That's with all else in the formula remaining equal, which it almost never does.