SPR (Stack-to-Pot Ratio) is the ratio between the effective stack size and the pot size, calculated by dividing the smallest stack still in the hand by the current pot. It determines how many pot-sized bets remain and shapes your entire post-flop strategy.
SPR fundamentally changes how you should play different hand types. With a low SPR of 1-3, you’re often committed with top pair and strong draws become less valuable since there’s little money left to win. Medium SPR situations (4-10) create the most complex decisions, where draws have good implied odds but you’re not automatically committed with one pair. High SPR spots (10+) favor speculative hands like suited connectors and small pairs that can win massive pots when they hit big.
The concept revolutionized tournament poker strategy when Ed Miller popularized it in “Professional No-Limit Hold’em.” Players realized that manipulating preflop sizing to create favorable SPRs was just as important as the cards themselves. A 3-bet that creates an SPR of 3 with pocket aces is ideal, while that same SPR with suited connectors is terrible.
How to Calculate SPR
The formula is straightforward: SPR = Effective Stack ÷ Pot Size. The effective stack is the smallest stack among players still in the hand.
Example 1: Basic Calculation
You have $200 in a $1/$2 game. Your opponent covers you. You raise to $6, your opponent calls. The pot is $13 ($6 + $6 + $1 small blind). Your SPR = $194 ÷ $13 = 14.9. This is a high SPR situation.
Example 2: Tournament Spot
Blinds are 500/1000. You have 15,000 chips, your opponent has 12,000. You raise to 2,500, they call. The pot is 6,500 (2,500 + 2,500 + 1,500 in blinds). The effective stack is 9,500 (opponent’s remaining chips). SPR = 9,500 ÷ 6,500 = 1.46. This is a low SPR where you’re committed with most made hands.
Practical Applications
Decision Making
SPR dictates your commitment threshold. With SPR under 2, you’re getting the right price to stack off with any overpair or top pair good kicker. The math: if SPR is 1 and you bet pot on the flop, you have exactly a pot-sized bet left for the turn. Your opponent needs only 33% equity to call profitably, meaning even draws are getting the right price.
EV Calculation
Consider SPR 3 with AA on K♠7♣2♦. You bet 2/3 pot, leaving SPR ~1 for the turn. If called:
EV = (0.85 × total pot) , (0.15 × stack invested)
With such low SPR, getting your stack in is almost always +EV with overpairs.
Solver Perspective
Solvers show that optimal 3-bet sizes often target specific SPRs. Against a button open, big blind 3-bets create:
- SPR 3-4 with value hands (AA-QQ)
- SPR 6-8 with middling hands (TT-99, AQ)
- SPR 10+ in single-raised pots with speculative hands
Common Shortcuts
The “Rule of 10”: Multiply the preflop pot by 10. If effective stacks are less than this, you have a low SPR situation. More than 10x = high SPR. Between 5-10x = medium SPR. This quick math helps with in-game decisions.
Interaction with Other Concepts
SPR connects directly with implied odds. High SPR means high implied odds for drawing hands. It also relates to reverse implied odds, high SPR with medium-strength hands like TPTK can be dangerous against tight ranges.
Pro Tip: In tournaments, use preflop sizing to manipulate SPR. If you have 25bb and face a 2.5bb open, a 9bb 3-bet creates an SPR of ~1.3 if called, perfect for committing with strong hands but terrible for speculative hands.
When Does SPR Matter?
SPR becomes critical in three main situations:
1. Multiway Pots: With three players and 100bb stacks, a 15bb pot creates SPR ~6 for each player. This medium SPR favors hands that can make the nuts, as one-pair hands face reverse implied odds.
2. 3-Bet Pots: These naturally create lower SPRs. A standard 3-bet to 10bb called creates a 21bb pot with 90bb behind (SPR ~4). This is why 3-betting with suited connectors requires careful planning.
3. Tournament Play: Short-stack situations constantly create low SPRs. With 20bb facing a min-raise, calling creates SPR ~8. But 3-betting to 6bb creates SPR ~1.5 if called, a massive strategic difference.
Common Mistakes with SPR
Playing draws aggressively in low SPR spots. With SPR 2, your flush draw has terrible implied odds. Even if you hit, there’s only 2 pot-sized bets left to win. The math doesn’t support aggressive play.
Overplaying one-pair hands in high SPR situations. With SPR 15 and TPTK, you’re not looking to play for stacks. The reverse implied odds are massive when deep.
Ignoring SPR when choosing preflop actions. Calling a 3-bet with 22 when it creates SPR 3 is burning money. You’ll never get paid enough when you hit your set.
Don’t Confuse With…
SPR vs pot odds: Pot odds tell you whether to call one bet. SPR tells you how the entire hand will play out across all streets.
SPR vs M-ratio: M-ratio (used in tournaments) measures your stack in terms of rounds you can survive. SPR measures your stack relative to the current pot.
Key Takeaway
SPR is your roadmap for post-flop play. Low SPR (under 4) means you’re committed with strong made hands and draws lose value. High SPR (over 10) favors speculative hands and requires caution with one-pair holdings. Master SPR manipulation through preflop sizing to create situations that favor your hand type.
