[In-Depth Explanation] What is SPR in poker?

What is SPR?

SPR, an acronym for Stack to Pot Ratios, translates in Japanese as ‘the ratio of the pot to the stack.’ It represents how much stack you have in relation to the pot and is one of the key metrics for deciding future play lines.

Calculation Method

To calculate SPR, it’s essential first to understand the Effective Stack.

Effective Stack

The maximum stack amount that can enter the pot henceforth.
For instance, if Player A and Player B are involved in the pot, and Player A has a stack of 100BB while Player B has 80BB, the Effective Stack is 80BB.
Next, the calculation of SPR is as follows:

SPR

Effective Stack / Pot Size
For example, in a pre-flop scenario where two players are involved and the pot is $20 with an effective stack of $100, the SPR is calculated as 100 ÷ 20 = 5, meaning the SPR is 5.

The Importance of SPR (Relation to Hands and Position)

SPR is essential for decision-making as it’s closely related to hand ranges and positions. By considering SPR in your actions, you can maximize profits and minimize losses.

SPR and Hand Range

• When SPR is High
  The value of ‘hands that can become nuts’ significantly increases, enhancing the value of speculative hands like low pocket pairs and suited connectors.

• When SPR is Low
  The value of hands that can become nuts decreases slightly, increasing the value of overpairs and top pairs.

SPR and Position

Poker inherently favors in-position (IP) play, but when SPR is high, position becomes even more advantageous than when it’s low.
This is because, with a high SPR, the value of nut-making hands increases, and the likelihood of seeing the turn and river cards is higher, allowing for advantageous action based on the opponent’s moves.

SPR and Bet Size

When SPR is high, bet sizes tend to be larger, and when it’s low, bet sizes tend to be smaller.
This is because the lower the SPR, the more important the concept of commitment becomes. In extreme cases of low SPR, a flexible approach with a strong commitment mindset is necessary.

Commitment

Refers to a situation where ‘betting all your chips still results in a positive expected value.’
A common scenario is when you hold a drawing hand against an opponent’s bet, and while you’re likely losing at the moment, the odds are high enough that you can’t afford to fold.

When SPR is High

The value of speculative hands like low pocket pairs and suited connectors increases.
Low pocket pairs can extract a lot of chips from an opponent’s overpairs or top pairs if a set is hit on the flop or turn.

Suited connectors become more valuable as the likelihood of seeing the turn or river cards increases, allowing for drawing strong hands like flushes or straights.

However, if the opponent holds a stronger set, straight, or flush, you risk losing all your chips, so overconfidence is dangerous.

Pre-flop when SPR is High

Pre-flop

When SPR is high, the size of pre-flop raises and 3-bets tends to increase. Additionally, you can call an opponent’s 3-bet wider than usual.
In this instance, a 3-bet of 17BB is made against a BTN’s 3BB open from the BB, a bit larger than the standard 4-5 times size.

Post-flop when SPR is High

Flop

While it depends on the situation, flop bet sizes tend to be larger when SPR is high. Using too small a bet size gives speculative hands in the opponent’s range sufficient odds, due to the high SPR.

In this case, BB has a top two pair and opts for a slightly larger than half-pot CB of 18BB, considering the higher-than-usual SPR.

When SPR is Low

The value of hands like overpairs and top pairs increases. With a low SPR, there’s a higher chance of going all-in on the flop or turn, allowing for effectively negating the opponent’s draw equity and extracting value from middle hits.

Pre-flop when SPR is Low

Pre-flop

When SPR is low, playing with a constant awareness of commitment is necessary.
In this example, a 9.5BB 3-bet is made against CO’s 2.5BB open from the SB with ❤Q❤J. A higher 3-bet like 12BB would force a commitment against a potential 4-bet all-in from CO, leaving no option but to call.

The 3-bet range is adjusted to allow playability against a call, prepare fold equity against a 4-bet all-in, and maximize range EV.
A 9.5BB size is chosen to avoid commitment against a 4-bet all-in, allowing a fold.

Post-flop when SPR is Low

Flop

Continued consideration of SPR is necessary post-flop.
SB has an open-ended straight draw and a backdoor flush draw, warranting a bet.
However, a small CB would lead to commitment against an all-in from the opponent.

Thus, going all-in on the flop is chosen, a slightly larger size, to maximize pressure on the opponent.

Summary

This chapter explained the calculation method and importance of SPR.
By considering SPR while deciding bet sizes and actions, you can maximize profits.
Be prepared to adapt appropriately whether SPR is high or low.