Expected Value (EV) in Sports Betting, Explained With Real Numbers
Expected value is the only number that decides whether a bet is good. What +EV actually means, how to compute it in your head, and why good bets lose all the time.
One number decides everything
Expected value is what a bet is worth on average if you could run it thousands of times. EV = (win probability × amount won) − (loss probability × amount staked). Positive EV means the price underpays the true risk in your favor; negative EV means you're the one overpaying.
Example: you bet $100 at +150 on an outcome you believe hits 45% of the time. EV = 0.45 × $150 − 0.55 × $100 = $67.50 − $55 = +$12.50. That's a +EV bet on a side that loses more often than it wins — which is the whole point. Good bets and likely winners are different things.
The break-even shortcut
Every price has a break-even probability — the implied probability from the odds. -110 needs 52.4% to break even. +200 needs 33.3%. -300 needs 75%. The entire EV question compresses to: is my estimate of the true probability above the break-even number?
This is also why the vig matters so much. At -110 you need 52.4%, not 50% — the book charges you 2.4 points of probability just to play. Every bit of vig you avoid through line shopping is pure EV added to every bet you make.
Why +EV bettors lose constantly (and profit anyway)
A bettor who only makes 45%-true-probability bets at +150 loses 55% of all bets forever — while making money forever. Individual results are noise around the average. The discomfort of this is exactly why most people can't bet this way: human brains score recent results, not long-run prices.
The practical defenses are boring and effective: flat, small stakes so no single loss matters; a written record of estimated probability versus price so you grade your process, not your luck; and CLV tracking as the fast feedback loop on whether your probability estimates beat the market's.
Frequently asked questions
What does +EV mean in betting?
Positive expected value — the odds pay more than the true probability requires. A +EV bet makes money on average even though it can lose (and often does) on any given day.
How do I know my probability estimate is right?
You never know for one game. Over many bets, track closing line value: if the market consistently moves toward your numbers, your estimates are beating the market's. If not, they aren't.
Can a bet on an underdog be better than a bet on a favorite?
Constantly. Value lives in the gap between price and probability, not in which team is better. A 40% underdog at +180 is a far better bet than a 70% favorite at -300.
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Keep reading
What -110, +150, and -200 actually mean, how to convert odds to implied probability, and why the difference between odds and probability is where all the money is.
What a unit is, why every serious bettor talks in units instead of dollars, how to pick your unit size, and when a bet deserves 1u, 2u, or 3u.
Closing line value is the most reliable measure of betting skill — more reliable than your win-loss record. Here's what CLV is, how to measure it, and why it predicts long-term profit.