Expected value (EV) is the one idea every winning bettor lives by: is this bet worth it at this price, over the long run?
The simple version
EV = (chance you win × what you win) − (chance you lose × what you lose)
Example: $100 at +150 (you win $150) on a team you think wins 45% of the time.
- 0.45 × $150 = $67.50
- 0.55 × $100 = $55
- EV = +$12.50
On average you'd make $12.50 per bet over many bets like this. That's a +EV bet.
Same bet, but you think they win 35%:
- 0.35 × $150 = $52.50
- 0.65 × $100 = $65
- EV = −$12.50. Skip it.
The shortcut
Convert the odds to implied probability. +150 → 40%.
- Your number above 40% → +EV
- Your number below 40% → −EV
Why it matters
+EV bets still lose often. A 45% bet loses more than half the time! But over hundreds of bets, +EV wins and −EV loses. One weekend of results means almost nothing.
Where +EV comes from
- Lines that are slow to react to news
- Differences between books (line shopping)
- Overreactions on prediction markets
- A better probability estimate than the market's, yours or your AI's
Key takeaways
- Bet the price, not the team
- +EV = your probability beats the implied one
- Judge yourself on process, not one weekend
The bottom line
You don't need to win every bet. You need to keep making bets where the math is on your side, and size them so a bad run doesn't knock you out.