EV (Expected Value) calculation is the fundamental operation of mathematical poker, summing each possible outcome multiplied by its probability. The basic formula is EV = (P_win × Pot) – (P_lose × Investment), but complex situations incorporate multiple streets, fold equity, and full range equity. Positive EV does not guarantee immediate results, only long-term profitability with sufficient sample sizes. Comparing EVs of different actions (bet vs check, call vs fold) is the correct method for making optimal decisions independent of short-term outcomes.