SPR (stack-to-pot ratio): how to calculate it and how it changes your plan for the hand

What SPR is and how to calculate it

SPR (stack-to-pot ratio) is:

SPR = effective stack / pot at the start of the street

You calculate it on the flop, using the effective stack (the shortest stack among players still in the hand) left after preflop action. The number matters for what it tells you: how many times the pot fits into what is left to bet.

With an SPR of 2, a pot-sized bet on the flop and another on the turn are enough to get all-in. With an SPR of 17.7 you would need very large bets on all three streets to get every chip in. That is why SPR ties together three things: your hand strength, your bet sizing and the moment your stack becomes committed.

Typical SPRs at 100 bb in 6-max cash

With a 2.5 bb open, a 7.5 bb in-position 3-bet and an 11 bb out-of-position 3-bet:

The pattern is clear: every preflop raise grows the pot and shrinks the stack behind, so SPR drops fast. A single-raised pot plays with high SPR; a 3-bet pot with medium or low SPR; a 4-bet pot with very low SPR.

Low, medium and high SPR: which hands stack off

At POKER AULA we use three bands to plan hands at 100 bb:

• Low SPR (under 4). A good top pair or an overpair is enough to get all-in. There is no room for pot control: once you bet, the next bet is nearly the whole stack.
• Medium SPR (4 to 10). A good top pair plays a big pot, but carefully against heavy aggression: a check-raise followed by a big turn bet usually means something better.
• High SPR (over 10). To stack off you want two pair, a set or better. Top pair is a hand to win a medium pot, not to put in 100 bb against an opponent who raises and re-raises.

This also changes which hands you want to take to the flop. With high SPR, hands that hit hard and get paid when they do gain value: small pairs for set mining, suited connectors. With low SPR those hands lose value and raw-equity hands such as big pairs and strong aces gain it, because you will almost always reach showdown.

3-bet pot example: SPR 3.96 with top pair

From the BB you 3-bet to 11 bb with A♥Q♦ and the BTN calls. Flop Q♠8♥4♣: 22.5 bb pot, 89 bb behind, SPR 3.96. You have top pair, top kicker.

If you bet 2/3 pot on every street:

1. Flop: you bet 15 bb and get called. Pot 52.5 bb, 74 bb behind.
2. Turn: you bet 35 bb and get called. Pot 122.5 bb, 39 bb behind.
3. River: the last 39 bb are less than a third of the pot (31.8%).

Two normal bets put the stack in. And if you bet 15 bb on the flop and your opponent shoves, you call 74 bb into a final pot of 200.5 bb: you need 74 / 200.5 = 36.9% equity. Against a player who also jams draws and worse hands there, AQ clears that easily. With low SPR you make the stack-off decision preflop, when you 3-bet a hand that makes strong top pairs.

Single-raised pot example: SPR 17.7 with the same hand

Now you open A♥Q♦ from the BTN, the BB calls and the flop is the same Q♠8♥4♣. Pot 5.5 bb, 97.5 bb behind, SPR 17.7.

Betting 2/3 pot on every street:

1. Flop: 3.67 bb. Pot 12.83 bb, 93.83 bb behind.
2. Turn: 8.56 bb. Pot 29.94 bb, 85.28 bb behind.
3. River: 19.96 bb. Pot 69.87 bb and 65.31 bb still behind.

To get 97.5 bb in over three streets you would have to bet 116% of the pot each time. If the BB check-raises the flop and bets big again on the turn, that money goes in because they want it in, and at high SPR that usually means two pair, a set or a very strong draw. That is why top pair calls and controls the pot here instead of re-raising: the same hand that stacks off in the 3-bet pot is a medium-strength hand in the single-raised pot.

Commitment and geometric sizing

Being pot committed means you have put in so much that folding to a shove would be a pricing mistake. SPR lets you see that moment coming: if after your flop bet the rest of the stack is less than one and a half pots, plan the hand as a stack-off.

To split the stack into equal parts there is a formula, geometric sizing: the pot fraction f that gets everything in over n streets satisfies (1 + 2f)ⁿ = 1 + 2 × SPR.

In the 4-bet pot with SPR 1.7: you bet 11 bb on the flop, the pot becomes 67 bb and the rest of the stack (67 bb) is a pot-sized bet on the turn.

Common SPR mistakes

• Using your own stack instead of the effective one. If you have 150 bb and your opponent 60 bb, SPR uses 60.
• Only thinking of SPR when you get raised. The plan is built on the flop, or earlier: which hands you 3-bet already decides the SPR you will play.
• Playing top pair the same way in every pot. It is a stack-off hand at SPR 3.96 and a medium-strength hand at SPR 17.7.
• Calling preflop to set mine with low SPR. At an SPR of 1.7 there are no chips left to win when you hit.

How to practice it

Before every flop, say the pot, the effective stack and the SPR out loud; after a few sessions it becomes automatic. In POKER AULA the Calculator gives you SPR and geometric sizing for any pot, and the Training mode puts you in single-raised and 3-bet pots where you decide whether to commit, with an explanation for every answer. SPR is taught in the Medium level and developed further in Upper Intermediate. If you want to try it, you get 48 hours free.