## Key Takeaways - Expected value (EV) is the average profit or loss per bet if you repeated the same wager many times. - The formula is EV = (win probability x profit per win) - (loss probability x stake). - Only positive-EV bets grow a bankroll over time; negative-EV bets slowly drain it. - Your EV is only as honest as your win-probability estimate, so be conservative and track results.

## What Expected Value Really Means Expected value answers one question: if I made this exact bet a thousand times, would I be up or down on average? It blends two things you can control: the price you take and your honest estimate of how often the bet wins. A bet at +100 odds where you win 55% of the time is profitable in the long run, even though you still lose 45 individual bets along the way. EV does not predict any single outcome; it describes the average. That distinction matters because bettors routinely confuse a lost bet with a bad bet. A positive-EV bet that loses was still the right decision, and a negative-EV bet that wins was still a mistake.

## The Formula With a Worked Example EV = (p x profit) - (q x stake), where p is win probability and q = 1 - p. Worked example: you bet $100 on a team at +120 (decimal 2.20), so a win profits $120. You estimate they win 50% of the time. EV = (0.50 x 120) - (0.50 x 100) = 60 - 50 = +$10. That is a positive expected value of ten dollars per bet on average. Now the same $100 at -110 (decimal 1.91) with a 50% estimate: EV = (0.50 x 91) - (0.50 x 100) = 45.50 - 50 = -$4.50. Same team, same confidence, different price: one bet grows your bankroll, the other quietly drains it. Price is everything.

## When to Use EV in Your Betting Use EV as the filter for every bet before you place it. If you cannot articulate a win probability and confirm the EV is positive, you are guessing, not betting with an edge. It is especially useful for comparing options: two books offering -105 versus -110 on the same side, or deciding whether a boosted promo price actually flips a bet from negative to positive. EV also pairs with stake sizing: bigger positive EV justifies bigger (but still disciplined) stakes, which is exactly what the Kelly Criterion formalizes. Build the habit of writing down your estimated probability before checking the odds, so the price cannot bias your judgment after the fact.

## Common EV Mistakes to Avoid The number one mistake is inflating your win probability to manufacture a positive EV, which is just optimism wearing a math costume. Keep a bet journal and compare your estimates against actual results to calibrate. Another error is forgetting the book's margin: most standard -110 lines are negative EV for a coin-flip estimate, which is why beating the closing line matters. Some bettors also treat one positive-EV result as a promise; variance means you can lose for weeks on genuinely good bets. That is normal and survivable only with proper bankroll management. Never bet money you cannot afford to lose, cap your session stakes in advance, and remember that no edge, however real, guarantees any individual outcome.

## Frequently Asked Questions **What is a good EV for a sports bet?** Any positive EV is theoretically good, but most recreational bettors target bets with at least a few percent edge, since small edges get eaten by estimation error. An EV of +5% or more on the stake is a solid find. **How do I estimate win probability?** Through handicapping: power ratings, matchup analysis, injury news, and historical data. Beginners can start by tracking closing-line value, since consistently beating the closing number is strong evidence your estimates are sharp. **Can EV be negative and the bet still worth taking?** Mathematically no, but entertainment bettors knowingly take negative-EV bets for fun, like lottery tickets. Just budget it as entertainment spending, not as an investment. **Does positive EV guarantee I will profit this month?** No. Positive EV plays out over hundreds of bets. Short-term losing streaks are expected even with a real edge, which is why bankroll discipline matters as much as the math.