What is Expected Value (EV) in Sports Betting? A Beginner Guide
The one concept that separates sharp bettors from everyone else—explained from scratch with a simple coin flip.
EV in Plain English
Expected Value (EV) answers a simple question: if I made this exact same bet a thousand times, would I come out ahead or behind?
Every bet you place has an expected value. If the math says you'll make money over the long run, the bet is positive EV (+EV). If the math says you'll lose money, the bet is negative EV (–EV). Casinos and sportsbooks are profitable because the vast majority of bets they offer are –EV for the bettor. Your job as a sharp bettor is to find the rare +EV opportunities.
The EV Formula
Here is the formula. It looks intimidating but it only uses basic arithmetic:
- Pwin = your estimated probability that the bet wins (expressed as a decimal, e.g., 50% = 0.50)
- Profit = how much you pocket if you win (not including your original stake coming back)
- Ploss = 1 − Pwin (the probability you lose)
- Stake = the amount of money you risk on the bet
If EV is positive, the bet is +EV. If EV is negative, the bet is –EV. That is the entire concept. The hard part is estimating Pwin accurately—but we will get to that.
The Coin Flip Example at +120 Odds
Let's make this concrete. Imagine a perfectly fair coin flip—50% heads, 50% tails. No skill, no analysis, just pure probability. Now imagine a sportsbook posts odds on "Heads" at +120.
Step 1: What does +120 mean?
American odds of +120 mean: if you bet $10 and win, you get $12 profit (plus your $10 stake back). Your total payout would be $22.
Step 2: What does the sportsbook think?
The implied probability of +120 odds is: 100 ÷ (120 + 100) = 100 ÷ 220 = 45.45%.
The sportsbook is pricing heads as if it only happens 45.45% of the time. But we know a fair coin lands heads 50% of the time. There is a gap between reality (50%) and what the book is pricing (45.45%). That gap is your edge.
Step 3: Calculate the EV
On average, you make $1.00 every time you place this bet. Not every time—you will lose plenty of individual flips—but over hundreds of repetitions, you converge on +$1.00 per bet. This is a +EV bet, and you should take it every single time it is offered.
What if the odds were –120 instead?
At –120, you risk $12 to win $10 profit. The implied probability is 120 ÷ (120 + 100) = 54.55%. The book is pricing heads at 54.55%, but the true probability is only 50%. You are paying more than the bet is worth.
This is a –EV bet. Over time, you lose a dollar per bet on average. This is how sportsbooks make money: they set odds where the implied probability exceeds the true probability, giving themselves a built-in edge (the "vig" or "juice").
Why +EV Matters
Most recreational bettors think in terms of "will this bet win?" Sharp bettors think in terms of "is this bet priced correctly?" The difference is everything.
- You do not need to win most of your bets. A bettor who wins 48% of +150 bets is profitable. A bettor who wins 53% of –110 bets is barely breaking even. The odds matter more than the win rate.
- The edge compounds over time. A 3% ROI on $500/week in total action is $15/week, or $780/year. Not life-changing, but it is positive. Scale up your bankroll and volume and those numbers grow.
- You can be wrong on individual bets and still profit. EV is about the aggregate, not any single wager. This is why bankroll management and volume are critical—you need enough bets for the math to play out.
- The sportsbook's closing line is the benchmark. If you consistently get better odds than the closing line (positive CLV), your process is working even during losing streaks.
How to Find Value Bets
Knowing the EV formula is the easy part. Finding real +EV opportunities is the actual skill. Here are the four practical methods:
1. Line Shopping
The single easiest way to improve your EV. Different sportsbooks post different odds on the same game. If DraftKings has the Lakers at +180 and FanDuel has them at +195, betting at FanDuel gives you better value on the identical outcome. Open accounts at 4–6 legal sportsbooks and compare prices before every bet. This costs nothing and immediately improves your results.
2. Exploiting Promotions and Odds Boosts
Sportsbooks regularly offer odds boosts (e.g., boosting a player prop from +200 to +280) as marketing promotions. Sometimes these boosts push a bet across the line from –EV to +EV. When they do, it is free money. You do not need a model or sophisticated analysis—just calculate whether the boosted odds imply a lower probability than the true likelihood of the event.
3. Building or Using a Model
More advanced bettors build projection models: statistical systems that estimate the true probability of outcomes based on data (team stats, player performance, injuries, weather, etc.). When your model says an event has a 55% chance of happening but the sportsbook is pricing it at 48% implied, you have found a +EV spot. Models require effort to build and maintain, but they are the most reliable path to a sustained edge.
4. Tracking Closing Line Value (CLV)
The closing line—the final odds before a game starts—is the sharpest price because it incorporates all market information. If you consistently bet at better odds than the closing line, you are beating the market. Track your CLV on every bet. Even during a losing stretch, positive CLV confirms your process is sound and profitability will follow over a larger sample.
Putting It All Together: Your Action Plan
- Open accounts at 4–6 sportsbooks (DraftKings, FanDuel, BetMGM, Caesars, etc.) for line shopping.
- Before every bet, calculate the implied probability of the odds and compare it to your estimated true probability.
- Only bet when your estimated probability exceeds the implied probability—that is, only bet +EV.
- Risk 1–2% of your bankroll per bet, never more. This protects you from variance.
- Track every bet: odds taken, stake, your estimated probability, the closing line, and the result.
- Review after 100+ bets. Are you getting positive CLV? If yes, keep going. If no, re-examine your probability estimates.
- Be patient. EV is a long-term game. You can lose 10 +EV bets in a row and still be doing everything right.
Frequently Asked Questions
What does Expected Value (EV) mean in sports betting?
EV is the average amount you expect to win or lose per bet over many repetitions. A +EV bet is one where the math says you profit long-term. The formula is: EV = (Win Probability x Profit) − (Loss Probability x Stake).
Can you give a simple EV example?
A fair coin flip at +120 odds. True probability = 50%. Implied probability = 45.45%. On a $10 bet: EV = (0.50 x $12) − (0.50 x $10) = +$1.00. You make $1 per bet on average. That is a +EV bet.
How do I find +EV bets?
Line shop across multiple sportsbooks, exploit odds boosts that cross into +EV, build or use projection models to estimate true probabilities, and track your closing line value (CLV) to verify your edge is real.
Does +EV betting guarantee profits?
No. EV is a long-term expectation, not a guarantee on any single bet. Variance means you will have losing streaks. The edge only materializes over hundreds of bets with disciplined bankroll management.
Before evaluating any sportsbook offer
Promotional headlines are less important than price quality, legal availability, responsible gambling controls, and whether the offer terms are clear enough to evaluate.
- Confirm the operator is licensed where you are physically located.
- Compare the full market: line, juice, settlement rules, and limits.
- Use deposit, loss, wager, and timeout tools before betting.
Responsible Gambling Reminder
Sports betting should be entertaining, not a source of financial stress. Never bet more than you can afford to lose. Set limits on your deposits, wagers, and time spent betting. If you or someone you know has a gambling problem, call 1-800-GAMBLER or visit the National Council on Problem Gambling at ncpgambling.org. You must be 21+ to place bets. Available where legally permitted.