For new bettors, “expected value” (EV) can sound like intimidating math jargon. In reality, it’s just a way of asking: If I made this bet a hundred times, would I come out ahead or behind? Every wager has two sides—the chance it wins and the payout you get if it does. Multiply those together, subtract the cost of losing, and you have EV. Negative EV means that over time, the bet drains your bankroll, even if you get lucky once in a while. Positive EV means that, with enough repetition, the odds tilt slightly in your favor. Sportsbooks build in margins to keep most bets negative EV for players, but by shopping lines, reacting faster than models, or finding mispriced props, you can sometimes flip the math. Thinking in EV shifts betting from emotion to process: less “gut feeling,” more long-term discipline.
Breaking EV Into Simple Parts
Let’s say you bet $100 on a coin flip that pays $200 if it lands on heads. The probability of winning is 50%. EV = (0.5 × $200) − (0.5 × $100) = $100 − $50 = +$50. That’s a positive EV bet because, on average, you gain $50 per play. If the payout were only $180 instead of $200, EV = (0.5 × $180) − (0.5 × $100) = $90 − $50 = −$10. Now it’s negative EV. The principle applies to every line you see in a sportsbook. The odds tell you what the book thinks the implied probability is; your job is to compare that to the true chance you believe the outcome has. If your estimate is higher than the implied probability, the bet is positive EV.
Here’s a simple comparison table:
| Bet Type | Stake | Payout Odds | True Win % | EV Result |
|---|---|---|---|---|
| Coin flip, pays $200 | $100 | +100 (2.0 dec) | 50% | +$50 (positive EV) |
| Coin flip, pays $180 | $100 | −110 (1.91 dec) | 50% | −$10 (negative EV) |
Where Positive EV Comes From
Positive EV isn’t luck—it’s about edges. Common sources include line shopping (finding a book that still offers +105 when the market moved to −110), props where you have inside data (a player’s injury history not fully priced in), or live markets where algorithms lag behind tempo shifts. Promotions and bonuses can also flip EV if rollover requirements are reasonable. The key is repetition. One positive EV bet doesn’t guarantee profit today; it guarantees that across hundreds of wagers, your bankroll will trend upward. Without volume and discipline, variance can mask value. That’s why professionals think in terms of long runs rather than single results.
Guardrails to Avoid Negative EV Traps
Sportsbooks rely on players ignoring EV. Flashy parlays, boosted odds with tight conditions, or bets on heavy favorites often hide steep negative EV. Responsible bettors keep guardrails: never bet without calculating implied probability, avoid markets where you lack information, and track closing line value (CLV) as a proxy for EV. If you consistently beat the market close, you’re likely finding positive EV. If not, you may be chasing narratives instead of edges. Another simple guardrail is setting stop-loss limits—no “doubling up” to recover from negative EV spots. A ledger with odds, stake, outcome, and your estimated probabilities helps expose leaks over time.
Turning Math Into Action
Expected value isn’t about solving equations on paper—it’s about decision-making in practice. Each time you consider a wager, ask: What’s the true chance this happens? and Do the odds offered give me more than that? If the answer is yes, it’s positive EV, and worth staking a small, consistent percentage of your bankroll. If no, pass—no matter how exciting the matchup. Over time, the discipline of only placing positive EV bets compounds like interest. Small edges add up, and bankroll swings smooth out. Betting stops being about lucky weekends and starts looking like a strategy.