Measuring Everything in Big Blinds
At stakes of $1/$2, a $200 stack equals 100 big blinds (bb). At stakes of $50/$100, that same 100 bb equals $10,000, yet the strategic decisions in the hand remain identical.
This is why poker players measure everything in big blinds: stacks, pots, and bet sizings. Thinking in bb removes emotional money pressure and allows skills to transfer seamlessly across any stake level. The standard cash game stack depth is 100 bb.
Effective Stack Size
You cannot win more from an opponent than they have in their stack. Nor can you lose more to an opponent than their current stack. Therefore, in a hand between two players, only the smaller of the two stacks is in play. This is termed the effective stack.
If you hold 150 bb and your opponent has 40 bb, the effective stack is 40 bb. Your extra 110 bb does not exist in this hand: you play as though both stacks were 40 bb.
SPR: Stack-to-Pot Ratio
SPR (Stack-to-Pot Ratio) is the ratio of the effective stack to the pot size on the flop:
It answers a simple question: how many pot-sized bets remain behind? At SPR 1, a single pot-sized bet commits all chips. At SPR 15, multiple large bets are required to get all-in, giving opponents ample room to define their hand strength.
Key takeaway: SPR is primarily determined by preflop action. Move the sliders in the tool below to observe how identical stacks yield radically different SPRs in single-raised versus 3-bet pots.
| Preflop Action (100 bb stacks) | Flop Pot | Flop SPR | Strategic Meaning |
|---|---|---|---|
| Single Raised Pot (Raise & Call) | ≈5.5 bb | ≈18 | Deep: one pair is insufficient to stack off |
| 3-Bet Pot (3-Bet & Call) | ≈20 bb | ≈4.5 | Medium: top pair becomes a major holding |
| 4-Bet Pot (4-Bet & Call) | ≈45 bb | ≈1.7 | Low: virtually any top pair or overpair commits |
Pot is large relative to remaining stacks. If you hit top pair with a good kicker or hold an overpair, prepare to commit your entire stack. Folding is unprofitable due to high pot odds.
Stacks are deep. One pair wins small pots but loses massive ones. High value shifts to sets, straights, flushes, and monster combo draws that can win stacks.