Expected Value (EV)
Every bet has an expected value, the average you'd win or lose if you could make it a thousand times. Once you start thinking in EV, betting stops feeling like gambling and starts feeling like investing.
What expected value is
Expected value, or EV, is the long-run average of a bet. A positive-EV bet makes money over time. A negative-EV bet loses it. You won't win every good bet, since variance is rough in the short run, but make enough of them and the math takes over. That's the whole reason casinos and books stay rich. They take negative-EV bets off customers all day.
The formula, in plain English
EV weighs what you win when you're right against what you lose when you're wrong, times how often each happens:
EV = (chance you win × profit if you win) minus (chance you lose × what you risk)
You bet $100 on a +120 dog that you think really wins 50% of the time.
Win: 0.50 × $120 = $60. Lose: 0.50 × $100 = $50. EV = 60 minus 50 = plus $10 a bet. That's positive EV. The price (+120 is about 45%) is paying you like the team wins less often than you think it does. Make that bet over and over and you average $10 a pop, even though you lose half of them.
Where the edge comes from
EV is only as good as your probability estimate. The positive EV shows up when your honest read on a game is higher than the price implies. That's why the earlier skills matter so much. Turn the odds into a probability, strip out the vig to get the fair number, and bet only when your number clears it. If your estimate is just a feeling, your "edge" is made up.
Thinking in EV changes everything
Once EV is how you see bets, the good habits fall into place by themselves. You stop caring whether one bet won, because a good bet that lost is still a good bet. You shop for the best number, because a better price raises the EV on the exact same wager. And you start grading yourself on decisions instead of last night's scoreboard. EV is the math sitting under every other strategy here.
Key takeaways
- EV is a bet's long-run average. Positive wins over time, negative loses, no matter what one bet does.
- EV = (win chance times profit) minus (loss chance times stake). Positive means the price is underrating your side.
- Your edge only exists if your estimate beats the price. Guessing doesn't count.
- Thinking in EV means grading decisions, not results, and always taking the best number.