Assume hero is playing a ring game with short stack. What is the smallest Stack Size you can 3bet a 3bb open raise without being committed. And what is the 3bet size to choose?
To be more concrete: 6max, CO open raise 3bb. Hero sits on the Button. I guess with 16BB there is no way to 3/bet fold. And even with a small 3bet (7bb?) hero would have 9bbs left and would be committed to the 17bb pot on every flop. So hero should alway shove preflop. But at which stack size is 3betting an option?
First, let's establish some parameters for what makes us pot-committed. Preflop, I like to stick with a 2-1 ratio, since the only way to be definitively more than 2-1 behind your opponent would be to know that his range is almost entirely made up of hands that have you dominated. We definitely know that this is not the case if we are short-stacked preflop.
So, we know that we aren't folding if we are getting 2:1 or better. From there, it can be a math problem dependent on the size of our 3-bet. Excluding dead money from blinds/antes/etc, we will be getting 2:1 any time our 3-bet is for 1/3 of our stack or more. I'd submit then that the smallest stack size you can ever 3-bet/fold is the one where you can make a meaningful 3bet for under 1/3 of your stack. "Meaningful" will depend on your opponent.
Opp bets 3bb, you 3bet to 7bb, and he shoves. If you have 21bb, then the effective pot at this point is 7bb from your raise + 7bb from his call + 14bb from the remaining effective stacksize in the shove = 28bb. Since it's 14bb to call and win 28bb, we must call.
The same ratio will hold for any size of 3bet; if we 3bet to 8bb, we need a stack of over 24bb to fold; 9bb, we need over 27bb; etc.
Estimate the equity your hand has vs their stackoff range, as soon as you are always getting better equity than the odds you are offered then you should not be 3bet/folding anymore.
Finding this point is a simple pot odds exercise combined with a bit of equity work with something like pokerstove.
Divide your stack by four, if the size of your 3bet is bigger than the result you will have an hard time folding your 3bet to a 4bet. If it's smaller then you can consider including bluff and some semi-bluff hands in your range.
That said, dont include bluffs in your range when your 3b represent 25% or more thank your stack, just play for value because you will have to fold too many times when you get 4betted and you'll be easily exploited as you will give anyone 25% of your stack for free every time.
