Why stack depth matters
A $300 stack means something different in a $1/$3 game than in a $2/$5 game. Poker strategy often describes stacks in big blinds because that normalizes the amount relative to the forced bet size.
Common reference points
20bb is short. 50bb is medium-short. 100bb is a common full-stack reference point. 150–200bb is increasingly deep. Actual room minimums and maximums can differ, so always check the venue's published buy-in rules.
Example: in a $1/$3 game, 100 big blinds equals $300. In a $2/$5 game, 100 big blinds equals $500.