Suggestion: bankroll calculator

I've noticed that this board fields a lot of questions about optimal bankroll size.

It's really easy to put together a simple spreadsheet (eg, for a palm pilot) that allows one to estimate the optimal bet size based on the formulas in PB (taking into account bankroll, house advantage, and true count). On mine, I included columns for half-, third- and quarter-Kelly with a nod to "Drawdowns for Proportional Betting" by Bill C. and Marc Ingenoso (www.bjmath.com).

You can use this spreadsheet to model the optimal bankroll size given a table minimum and house edge. As a new player, I've found it very instructive to play around with these figures; it's easy for us new guys to seriously underestimate bankroll requirements. Maybe we should post something like this on the BJ Reference page, either in the form of a download or an HTML form.

Most will find it easier to just get a tool like BJRM. But if you have the right info, including the frequency, advantage, and SD for each true count, then you can easily construct the spreadsheet. You need seven columns to start: TC, Freq, Adv, SD, BET, Expectation, Variance. You should express freq and adv as decimals. The first column (A) is simply the true count. Column E is the bet expressed in units. Col F is the expectation and is equal to B*C*E. Column D is the standard deviation for that true count. If your simulation doesn't give you this then use the generic 1.15. Col G is the variance and is equal to: B*D^2*E^2.

At the bottom you take the sum of columns. Make sure that col B totals to 1. The sum of Col F will be your win per round. The sum of Col G will be the variance. Take the square root of the sum of Col G to find your average standard deviation per round.

Now you have the basic information you need, the win per round and SD per round. You can designate other cells to put formulas for DI, SCORE, or ROR by referencing back to these. You can find optimal bet ramps by manipulating bet sizes in column E to maximize DI. With the basic information you will have here you can customize your calcultor using readily available formulas.

DI=(sum col f/ sqrt(sum col g))*1000

The value formerly known as SCORE= DI^2.

When you have manipulated the bets to maximize these values you will have an optimal ramp, and optimal Kelly bets.

If you want to find the optimal Kelly bank size you just use:
Bank=1/(sum col f/sum col g). That's essentially a fraction equal to ev/var. To find the optimal unit size you divide your total funds by the number of units in the optimal bank. For half Kelly you'd just double the number of units in the optimal bank, etc.

Enjoy