Effective stack
The effective stack is the smaller of the two stacks in a pot, because that is the most either player can actually win or lose in the hand.
It is the number that matters, and it is not the number on your own seat. Sitting with 300 big blinds against an opponent who has 40 is a 40 big blind hand, and playing it as though it were deep is the common mistake.
Everything that depends on stack depth depends on this figure: implied odds, the stack to pot ratio, and whether a hand can profitably chase a draw. In a multiway pot each opponent gives you a different effective stack.
an example
your cards
You have 200 big blinds and the player who raises has 35. The hand is worth at most 35 to either of you, so the deep stack buys nothing, and ace king is now a hand that is happy to get all the money in before the flop.
This example is made up. The real one is in your own hand history: find effective stack in your own hands and see how often it came up and what it cost you.
related terms
Stack
Your stack is the chips you have in play, which is the maximum you can win or lose in any single hand.
Stack to pot ratio
Stack to pot ratio, or SPR, is the smaller of the two remaining stacks divided by the size of the pot at the start of a ...
Short stack
A stack is short when it is small relative to the blinds, usually under about 30 big blinds, which removes most of the r ...
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Knowing the word is not the same as seeing it.
Forty hands against a bot, no account, and your own hand history at the end.