What is SPR?

Recently I've noticed thread around that have statements like "Top pair with a SPR of 5.1 is good"

What is SPR?

Stack to pot ratio. Mentioned (maybe coined?) in Ed Miller's Professional No-Limit Holdem.

I have yet to pick the book up, but SPR (or committedness) is a HUGE concept in ring games/deep stacked games period.

As Chuck said it's stack to pot ratio and is a huge topic in Professional No-Limit Holdem. Specifically it's the ratio of the total preflop pot to the effective remaining stack. So if you're playing a NL100 game (with $100 effective stacks) and raise from the sb to $5 and get called by the bb the SPR for this hand is 9.5 ($95 remaining to $10 preflop pot).

The authors suggest using SPR to plan your hands around commitment (or to avoid commitment). Against average opponents they suggest that you should generally commit with TP if your SPR is 4 (or below). That's 2 pot sized bets (preflop pot = 1P, so 1P on flop and 3P on turn). They also say that a SPR of 13 is BAD for TP hands, because that's 3 pot sized bets (river would be 9x the preflop pot) and they say that in general TP hands perform poorly in these situations because they cause TP hands to make poor decisions. Either committing too much with TP or folding the best hand to a big raise on the river.

It's an interesting concept and definitely makes you think more about your hand and how it may play out before you ever put a chip in the middle. I do recommend reading it but if you're a thick as I am it will take several reads before the concepts really start to make sense.