What is positive EV betting?

Positive EV betting means betting only when a price pays more than the outcome's fair odds. EV is short for expected value: the average profit or loss a bet would return if you could place it many times at the same price. A +EV bet is estimated to make money on average, but any single bet still wins or loses, and the estimate is only as good as the fair probability behind it.

How it works

Expected value weighs what you win by how often you win, and what you lose by how often you lose:

EV = (win probability × profit if it wins) − (loss probability × stake)

Per dollar staked, using decimal odds, that simplifies to:

EV% = (win probability × decimal odds − 1) × 100

Worked example. Say you estimate a side has a 45% chance to win, and a book offers it at +140.

1. Convert the price. +140 is decimal 1 + 140 / 100 = 2.40. Its implied probability is 100 / (140 + 100) = 41.67%. That is the win rate you need to break even.
2. Compare. Your 45% is above the 41.67% break-even rate, so the price beats fair. The fair price for a 45% chance is decimal 1 / 0.45 = 2.22, about +122.
3. Calculate. On a $100 stake: 0.45 × $140 − 0.55 × $100 = $63 − $55 = $8. Per dollar: 0.45 × 2.40 − 1 = 0.08, or +8% EV.

Now take the same 45% outcome at +110 (decimal 2.10): 0.45 × 2.10 − 1 = −0.055, or −5.5% EV. Same side, same chance, different price. Positive EV is about the price you get, not about picking winners.

The $8 is an average across many bets like this one. On this bet you either win $140 or lose $100.

How to find +EV bets

The hard part is the fair probability. Most +EV bettors don't build it from scratch. They take it from a sharp, low-margin market and compare it with prices at other books.

1. Pick a reference market. Choose a book or exchange whose prices you trust as an estimate of fair odds, and get both sides of the market you want to bet.
2. Remove the vig. Convert both sides to implied probabilities and scale them so they add up to 100%. The result is each side's fair probability. How to remove the vig walks through it, or use the no-vig calculator.
3. Shop the same bet. Find the same side, the same line and the same settlement rules at other books.
4. Compare and calculate. If a book's implied probability is lower than your fair probability, the price is +EV. Enter the stake, odds and fair probability in the expected value calculator to see the dollar figure.
5. Check before you bet. Confirm the price is still there, place the bet, and record the price you actually got.
6. Size it. Bet a consistent amount, or a fraction of Kelly with the Kelly calculator, so one loss doesn't dent your bankroll.

Doing this by hand works for one bet. Doing it across every line at every book is a job for a scanner.

Using Unjuiced

The Positive EV scanner does steps 1 to 4 for you. It devigs both sides of a sharp market to get fair odds, then ranks every opportunity by EV % with the best book, the sharp price, the fair odds and a recommended stake.

• Reference: Pinnacle by default. You can switch to Circa, BetOnline, a prediction market such as Novig, or any sportsbook, or build a custom weighted model.
• Devig method: Power, Multiplicative, Additive or Probit.
• Sizing: set your bankroll and a Kelly percentage, and each play gets a recommended stake.

Because it devigs, Positive EV needs both sides of a market to be offered. The Positive EV guide covers its settings and outputs. The expected value and no-vig calculators are free and need no account.

Mistakes to avoid

• Treating EV as a promise. +8% EV doesn't mean you make $8 on this bet. Results swing widely, and a few dozen bets tell you very little. Judge the process over hundreds of bets.
• Trusting the estimate too much. A fair probability is an estimate from a reference market, not the true chance. In the example, if the real chance is 41% rather than 45%, the same +140 bet is 0.41 × 2.40 − 1 = −0.016, or −1.6% EV. Thin edges vanish with small errors.
• Betting stale prices. Books and the reference market both move. An edge you saw a minute ago may be gone, or may have existed only because one book hadn't updated yet. Recalculate at the price you get.
• Comparing different bets. -3 and -3.5 are different markets. So are props with different rules for overtime or a player who doesn't play. Only compare the same line under the same settlement rules.
• Believing huge numbers. A very large EV on a popular market is more often a wrong line, a stale quote or a data error than a real edge. Check it at the book first.
• Ignoring limits. A book can cap how much you bet at a price, and an edge you can only bet a few dollars on is worth less. An unknown limit is not an unlimited one.
• Oversizing. Kelly sizing assumes your probability is right. Many bettors use half or quarter Kelly to absorb estimation error.

Track closing line value alongside your results. Regularly beating the closing price is a quicker read on whether your fair-odds source is any good than profit over a short run, though neither one proves future returns.

Questions

What does +EV mean in sports betting?

+EV, or positive expected value, means a bet's price pays more than its fair odds, so the bet is estimated to return a profit on average over many similar bets. It describes the price relative to the outcome's true chance, not whether this particular bet will win.

How do you calculate the expected value of a bet?

Multiply your estimated win probability by the decimal odds and subtract 1; the result is the expected profit per dollar staked. For example, a 45% chance at +140 (decimal 2.40) gives 0.45 × 2.40 − 1 = 0.08, or +8% EV.

Can a positive EV bet lose?

Yes. EV is an average across many bets, and a single +EV bet still wins or loses like any other. A side with a 45% chance loses 55% of the time even at a good price; the edge only shows up over a large number of bets.

Is positive EV betting profitable in the long run?

It can be, if your fair-probability estimates are accurate and you can bet the prices you find at a meaningful size. Estimation error, stale prices, betting limits and normal variance all cut into results, so +EV betting is a method with an expected edge, not a promise of profit.

What is the best positive EV betting tool?

Look for a tool that devigs both sides of a sharp reference market, lets you change the reference and the devig method, and shows the fair odds next to the offered price so you can check its work. Unjuiced's Positive EV scanner does this on Pro and Syndicate, and its expected value and no-vig calculators are free for checking a single bet by hand.