May 29, 2010
Better Betting 2 - Bet Sizing Calculator (Long Overdue)
A long time ago I wrote an introductory post addressing some technical aspects of bet-sizing, with an emphasis of betting to get all-in by the river. I introduced alpha, α as the ratio of the bet-size to the current pot.Â
A quick reminder:
 A pot-sized bet has an α of 1. A half-pot-sized bet has an α of 0.5. When the SPR is 13 we can make a series of three bets with an α of 1, concluding with a final all-in bet. For example, with a $130 stack and a $10 pot, we can bet pot on the flop, turn and bet all-in for pot on the river ($10, $30 and $100 bets).
Calculating appropriate bet sizes when the pot-to-stack ratio (PSR) is not 1, 4 or 13 is not simple. For example, with a PSR of 7 it is not immediately obvious what fraction of the pot to bet, given that you want to be all-in in three streets with the same α on each street. In order to assist those who are interested in these calculations, I wrote a little spreadsheet that can instruct you of these "perfect α" bet-sizes. You can "Save a Copy" if you want to enter your own values (you will need a Google account).Â
In itself, betting with equal α on each street isn't *that* important. However, a few minutes spent with the calculator establishing the SPR that make it awkward to get all-in over 2- or 3- streets can be of great use when planning a hand preflop, or deciding on your bet or raise sizing in general.  One great example would be re-raising an unpaired high-card hand preflop, a situation in which we are deliberately bloating the pot so that if we hit top pair we can get all-in easily with three smallish bets, or, if we choose, two larger ones. Certain SPR make this a lot easier than others; there are many variables to consider, but these ideas can all be contained within one question, "What will the SPR be if I get called?". It might be worth playing around with the calculator and thinking about your raise sizing, so you can plan your postflop bet sizes in advance.
5 Comments:
jjd323 posted on May 29, 2010 at 19:02 PM
You can check if you are using the calculator correctly: the 2-street alpha for a PSR of 7 is 1.44; the 3-street value is 0.73 (roughly speaking, a series of three 3/4 pot-size bets).
Slowjoe posted on May 30, 2010 at 16:07 PM
I think that you should use a different name from alpha for this, since alpha is defined as a constant in Maths of Poker with the value p/(1+p).
Perhaps you could use rho for ratio?
jjd323 posted on May 31, 2010 at 18:35 PM
Slowjoe, I'm aware of the alternative usage of α in MoP. However, given the provision of a clear definition for my parameter, and its limited usage outside the context of this discussion (so far, confined to my blogspace), I'll stick with α. Also, without wanting to nit too greatly on your comment - α, as defined by Chen and Ankerman, is not a constant - rather, it is a variable in p. Furthermore, I don't know the alt-code for rho (Ï).
Slowjoe posted on June 03, 2010 at 17:18 PM
Ok, thanks for considering the suggestion. And my bad re: the constant. Had a brainstorm.
I think that what you are doing is quite useful, and so likely to leave your blog-space.
jjd323 posted on June 03, 2010 at 19:10 PM
SlowJoe, maybe it would be a good idea to contact me via Skype - same username as on DC. We can chat about the future articles. It would be useful for me to bounce ideas of an interested party before I publish them.
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