[AleoMagus]

Here is the actual ROR calculation if you want to mess around with the numbers (though this may be easier to just do with one of the many SD/ROR calculating spreadsheets)

B = -(SD^2/2W)LN(r)

r = EXP(-2WB/SD^2)

where,
W is your profit/tourney ($)
SD is your standard deviation ($)
r is your desired risk of ruin
B is your bankroll ($)

Regards
Brad S

Edit: This thread brings up a couple additional points which are important:

As multi-tabling players typically have a smaller ROI, bigger bankroll is needed. As high stakes players typically have a smaller ROI, bigger bankroll is needed

If players are willing to step down in stakes as they diminish their bankroll (so as to always stay at a certain number of buy-ins) they can significantly reduce their risk of ruin because they effectively are playing with multiple bankrolls. They would figure their ROR for half (or whatever) of their actual bankroll at the level they are playing, then multiply that by another ROR for half of that remaining bankroll at a lower stake, and so on. In this way, 20% ROR at $109 followed by 20% ROR at 50+5, followed by 20% ROR at 30+3 etc... will actually turn out to be a very very small ROR.

What this means is that you can actually maximize profit by playing at higher stakes, and still maintain a very small ROR as long as you are willing to step down when things run badly. It is worth noting that this is psychologically very difficult. you will experience big swings upward this way, which will often crash down again but become 'compressed' as you drop in stakes. Fun