Since I realize I have no clue how to utilize the qfit calculator tools, I decided to ask here. I am planning on having $75 as my average bet. I want to play for 4 hours which I estimate to be 320 hands. The win rate is likely -$0.50 per hand. I believe the standard deviation is $1529 ( 1.14 x 75 x sqrt(320) ). My question is how do I calculate the odds of going bankrupt given x where x is the amount of money I bring? My friend tells me that $1529 does not mean a 16% ROR ( (100-68) /2 ) where $1529 is the given bankroll, because I thought bringing $1529 means not tapping out 16% of the time. Can someone clarify? Thanks in advance.

Assuming that you are playing basic strategy on a typical blackjack game, your calculation of the standard deviation is correct for flat betting. There is approximately a 16% chance that you will be down by one standard deviation or more after 320 hands, but that does not mean your risk of ruin is 16% percent because that includes scenarios where you lose more than that and then make a comeback. Your RoR will be somewhat higher. Risk of Ruin is described in great detail in Don Schlesinger's book Blackjack Attack 3rd Edition (BJA3). What problems are you having with the QFIT calculators?

I see that your friend posted the same question on blackjacktheforum.com. It also looks like Don Schlesinger answered him personally. You would both do well to listen to him. He has forgotten more about blackjack than most of us have ever known.

That's the problem I'm having.... I need to know my RoR bec it does me no good to know that I could be down MORE then my bankroll of $1500 in a period of 4 hrs only to "make a comeback" since I'd already be bankrupt at that point in time! Could you calculate my RoR in this specific scenario? Not gonna buy a book when it's just the RoR I need. (I have 0 interest counting and am up significantly lifetime NOT counting so def not about to start!) And btw the house edge for me when I play at H17/NS tables is 0.57%, 0.28% when I play in LV (but since I always employ offensive/defensive hand interaction it's def lower) & not 0.67%... Thanks