Definition
Stack-to-Pot Ratio (SPR) is calculated by dividing the effective stack size (the smaller of all stacks in the hand) by the pot size on the flop. It is a fundamental concept in post-flop poker that helps determine how strong a hand needs to be to commit all chips to the pot.
Low SPR (1–3): Stacks are shallow relative to the pot. You are "committed" with strong top-pair and drawing hands. Even weak made hands become calling hands because the pot odds when getting all-in are too good to fold.
Medium SPR (4–10): The most common and complex range. Decision-making requires careful consideration of hand strength, draws, and implied odds.
High SPR (10+): Deep-stacked play. Only very strong hands (sets, two pair on dry boards, straights, flushes) are strong enough to go all-in comfortably. Top pair hands lose value significantly in high-SPR spots.
Example
In a 3-bet pot where the flop pot is $90 and effective stacks are $250, SPR = 250/90 ≈ 2.8. At this SPR, top pair/top kicker is a strong enough hand to play for stacks if the board is dry. You should not be looking to fold top pair in a low-SPR spot.