SPR can also be considered the ratio of risk : reward. To put it another way, in this example the remaining effective stack sizes are 6.3 times the size of the pot. If both you and your opponent have $100 in your stack, the stack to pot ratio would be: One opponent calls on the button and both of the blinds fold. Let's say you raise to $6 in MP before the flop in a $1/$2 NL cash game.
SPR is the effective stack sizes divided by the size of the pot on the flop. I highly recommend you buy the book to feel the full force of 70 pages worth of SPR euphoria. This article is merely a brief introduction and overview of SPR. In this article I aim to explain the basics of SPR in poker and show you how it can be used to make your post-flop decisions a lot easier in cash games. The stack-to-pot ratio (or SPR for short) principle was coined by Ed Miller in the book Professional No-Limit Hold'em: Volume I. There's also a handy classroom section on SPR starting at 6:26 in SplitSuit's 'Playing AA' video.
