Stack-to-pot ratio (SPR)

SPR tells you how much stack is left to play with relative to the pot at the start of a street, usually the flop. It uses the effective stack, the smaller of the two remaining stacks, because that is the most either player can win or lose.

SPR = effective stack / pot

A simple set of bands helps read the number quickly: low is under 4, medium runs from 4 to 6 inclusive, and high is anything over 6.

Worked example. The pot is 20bb going to the flop and the effective stack behind is 80bb:

SPR = 80 / 20 = 4

That sits right at the boundary between low and medium. Nudge the pot up a little, or the stacks down, and the hand slides into the low band, where commitment becomes close to automatic for a strong made hand.

A low SPR favours commitment: with little room left behind, a strong pair or better can get all in without much agonising, since there is not enough depth to be outdrawn expensively. A high SPR rewards playability and position instead, since deep stacks behind pay off draws and disguised hands, while one pair alone becomes fragile. You mostly set the SPR yourself before the flop, since every preflop raise and call shrinks the room left behind it.