Ok so I know that stack sizes are important especially in sng's and tourneys when the blinds are high, but I don't fully get why it matters so much with say 100bb deep to 300bb deep. I mean if you have enough manoeuvrability to fire at 3 streets or call 3 streets how would the player with 300bb deep have such a big advantage? Also Im talking cash games right now not sng's.

I'm sure there's a logical reason so this is a bit of a noob question but could someone give an example with the stack sizes 100bb-300bb, thanks.

deeper stacked = more play left = push your edge

if you have 300bb and villain has 100bb eff stacks are 100bb and therefore it doesnt give you advantage that youre deeper than him

what if it were 100-50?

then eff stacks are 50bb which is shortstacked poker
it doesnt matter if you have 100000000000000000bb to his 50bb or you have 50.00001bb to his 50bb

Stack 'leverage' is part of the answer.

The more money behind, the more often you're going to be able to put me in crappy spots when you bet the turn (say, esp IP). I know that if I call with a marginal holding you're often firing big on the river. So a relatively small bet on one street threatens major damage to my stack. With less behind I can more often commit very comfortably earlier in the hand.

So is it just a mental thing? I mean is there some sort of mathematical explanation as to why its a disadvantage for the short stack?

Well, there isn't a short stack.

If we're playing 300bb deep, then we both have 300bb, but in general, the more behind, the more your positional advantage counts. For a relatively small cost you're often going to be able to ask me if I want to play for stacks. And the answer is very often going to be no thanks.

lmao Im having trouble catching onto this but i somewhat understand thanks

your stacksize doesnt matter AT ALL

only effective stacksize matters in a hand as i said before

so there is no advantage then?

Do you understand what is meant by 'effective stack'?

You have 100bb
I have 30bb
Effective stack = 30bb

You have 600bb
I have 100bb
Effective stack = 100bb

You have 500bb
I have 300bb
Effective stack = 300bb

Only in that final case would we be playing deep.
And in that case, the positional advantage is magnified.

EDIT: OK, 'deep' is a relative term but these days, with 100bb buy-in so standard, you need to get above that before anyone's going to start saying 'wow, this is deep!'

if i understood your question correctly, no there is not

the better player has an advantage

The only advantage of having a deep stack is against other deep stacks if you have an edge over the player in a game that deep.

I know what eff stack is its just that I was reading in a book how important stack sizes are in a cash game so I was just wondering why its such a big deal

It's important to be aware of everyone's stack sizes because it can affect how THEY play. Like if someone's a short stack to your left, you need to be aware that he's looking to shove light, so you might tighten up a little (just quick example that's not 100% right, but just sayin')

*edit* also stack to pot ratio stuff comes into play, but that sounds a bit advanced for this thread

I think what deeepz is answering a different question. If I understand what you're asking it is, is it advantageous to play a deepstack game over a shortstack game? Well if you have a huge edge over your opponent then yes because that just means there is more money on the table. However I think the answer you are looking for is that the games are just played differently. In a shortstack game the relative strength of a hand is a lot higher than a deep stacked game. For example if I was in a game that is 20BB effective then I feel perfectly fine going all in with TPTK. However if I'm in a game that is 300BB effective than I am generally not stacking off with TPTK. The reasoning for this is SPR. If you search for SPR and research on that I believe that it will help answer your question.

Postflop in a cash game the stack to pot ratio is more important than overall stack sizes.

Preflop the effective stack size can make 3/4/5 bet ranges much different than a 100bb game, though. Imagine if you were sitting 600bb deep with an aggressive tourist in a 1/2 game and he made a standard for the table $10 open... you're pretty much gonna 3bet the entire range of hands you're playing, right? Because if you flop a set or whatever he's likely not gonna put his whole stack into a pot that's only $40 on the flop, but he might into a $200 one.

Stack sizes affect what hands you play and how much you will call to play them.

Ok this is the the most helpful answer, thanks for the other answers too I'm starting to get it now

Since you guys brought up SPR I remember reading about that a while ago saying something like the higher the spr the more luck matter and the lower the less it matters... something like that right? why is this?

There's also the idea that "nutty" hands get better as the stacks get deeper, i.e., it's more valuable to have JTs or Axs than, say, 22 with super deep stacks, because they're the nut high hand more often by the river and so you're going to be more willing to bet or call hundreds or thousands of blinds on the river with those hands than a set.

So that changes your hand selection somewhat, especially from early position.