What are Effective Stack Sizes?

Whenever you see somebody talk about a poker hand on forums, you might see them mention the term “effective stack sizes.” Like most poker lingo, this phrase isn’t immediately clear when you first see it. But the basic definition of effective stack sizes is pretty easy to explain since it’s just the smaller stack in […]

Whenever you see somebody talk about a poker hand on forums, you might see them mention the term “effective stack sizes.” Like most poker lingo, this phrase isn’t immediately clear when you first see it. But the basic definition of effective stack sizes is pretty easy to explain since it’s just the smaller stack in a heads-up situation. For instance, if Player A has 6,000 chips, and Player B has 3,000 chips, the effective stack size is 3,000 chips. Obviously just knowing this isn’t going to improve your game much, so let’s go a little more in-depth.

The reason why people talk about effective stack sizes is because it helps a bigger stack think about what move they’re going to make based on who they’re calling/raising. For example, let’s say that you want to play for a flush with Jh-Th on a board of 9h-Ks-7h. You have about a 4.2:1 chance of hitting the flush on the turn, which means you should have better pots odds than this. Even if you are going for implied value here, you should have around 5:1 pot odds on the call. So let’s say that the call is 200 chips and the pot is 900 chips.

Even without good enough pot odds in the aforementioned scenario (4.5:1), you could probably call on the turn since you stand to earn a lot of chips if you hit the flush. But what if your chip stack is 2,000, and your opponent’s remaining stack after the 200-chip raise is only 500 chips? In this case, the effective stack of 500 chips is not enough to justify calling. You aren’t getting good pot odds in this situation (the pot would need to be less than 1,300 chips for good pot odds), so you should fold based on the effective stack principle.

So next time you’re the bigger stack in a heads-up situation, you should keep effective stack sizes in mind when you’re deciding on calling.

 

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