NL holdem is a game of implied odds. We should not make pre-flop decisions based solely on pot odds unless we are going all-in.
If we complete the SB with garbage hands, we have to flop 2 pairs or better to be able to continue post-flop with any confidence.
The odds to flop 2 pairs is 2.0%
The odds to flop trips is 1.3%
The odds to flop full house is 0.1%
This gives us combined odds of 3.4% for a good flop.
However, we will sometimes lose with 2 pairs when the board counterfits us or when there are multiple players and one makes better 2 pairs by the river. We will also sometimes lose with trips to str8s or flushes. So we have to discount the 3.4%.
If we lose say 0.45% of the time, then 0.45% of our wins will pay for that and we are left with an estimated chance to win of 2.5% which is 40 to 1 odds.
We also have to account for the fact that the BB will sometimes raise after we complete and we will have to fold. Say that this happens 20% of the time. This increases our effective cost to
EffCost = 0.5BB * 100/(100-%raised) = 0.625 BB
Since our odds to win are 40 to 1, we need to make a minimum average profit of
RequiredAvgProfit = odds*cost = 25 BB
From the calculations above, we can make the following observations:
- When heads up, this would require betting on all 3 future rounds. Since we are OOP, we don't have the luxury of our opponent leading into us. It is very unlikely that everytime we hit, our single opponent will call us down all the way to the river.
- With multiple opponents, it is more likely to have an average win of 25 BB because the initial pot is larger and because it is more likely that someone flopped something good.
- When blinds are small and stacks large, we can apply the same critiria as for cash games
- When blinds are medium, the average stack is in the 20-30BB area. So it is very unrealistic that everytime we hit the flop we will stack someone.
- When blinds are big, the situation is ever worse since many players will have stacks less than our minimum average win requirement of 25BB. In addition, completing the small blind represents a larger % of our stack. To top it all off, when stacks are shorter, it is more likely that the BB will re-raise us, which further reduces our odds.
In conclusion, we can complete the small blind in cash games or early in a tournament if there are multiple limpers.