To calculate runner runner odds:
First calculate the odds of getting the first card needed for the runner. The easiest way of doing this in your head is figuring how many "outs" you have and taking that number times two. That's not an exact percentage, but it gets you close.
Then figure your percentage of getting the second card needed for the runner. Same procedure.
After you work both of these numbers, you take the two percentages TIMES each other... for instance, if you have a 8% chance of getting the first card, and assuming you get that one, you have another 8% chance of getting the second, you take:
8/100 * 8/100 = 64/1000. Reduce that fraction to
6.4/100, or 6.4%. There's your odds.
