What is a +EV player prop?
Short answer: A prop is +EV (positive expected value) when your side's real chance of winning is higher than the chance its price implies. Since nobody knows the real chance, bettors estimate it, most often with a sharper book's no-vig price: if that says 55% and the price you can bet implies 52%, the bet looks +EV by that estimate. It is an estimate, not a guarantee.
Expected value in one line
Expected value is what a bet returns on average if you could place it many times: (chance of winning × amount won) − (chance of losing × stake). It is positive when the chance of winning is higher than the price assumes.
A worked example
You can bet an under at -110, which implies 52.4%. If the true chance is 55%, a $100 bet returns on average 0.55 × $90.91 − 0.45 × $100 = +$5.00. If the true chance is 50%, it returns −$4.55. Everything depends on that true chance, which nobody knows.
How bettors estimate the true chance
The common shortcut is a sharper book's no-vig probability, usually Pinnacle's (see why). If Pinnacle's no-vig says 55% and DraftKings' price on the same line implies 52%, the DraftKings side looks +EV by that estimate.
Why "+EV" screens mislead
- The estimate is not the truth. If the sharper book is wrong or slow, the "edge" is an illusion.
- Not every gap is equal. In OpenSlate's research, Overs that look cheap against Pinnacle have lost money; we call them Trap Overs.
- Prices move. A gap measured an hour ago may be gone by the time you look (see how often lines move).
- Small samples are noise. A +EV estimate is about averages over hundreds of bets, not tonight's result.
OpenSlate shows the measurement, both books' prices and the no-vig gap, on tonight's props. It does not tell you what to bet.
EV versus results
A bet with positive expected value can lose, and a bet with negative expected value can win. On a single prop the result is close to a coin flip, so tonight's outcome says almost nothing about whether the price was good. Expected value only shows up over a large number of bets, which is why bettors who take EV seriously track the price they got against the closing price (see what CLV tells you) rather than judging themselves on wins and losses.
Where the "true probability" comes from matters
Every +EV claim rests on someone's estimate. A sharp book's no-vig price is a reasonable starting point; a model built on recent games is another; a hunch is a third. Each can be wrong, and a tool that labels a bet "+EV" is only as good as the estimate underneath it. OpenSlate shows the inputs, both books' prices and the gap, so you can see what the estimate is based on instead of trusting a label.
Related questions
- Why do DraftKings and Pinnacle lines differ?: the business, timing and news reasons two books disagree on the same line.
- What is a Trap Over?: why a cheap-looking Over is listed apart instead of treated as value.
- Are NBA rebound unders profitable?: an honest answer, and how to judge any claim that a market wins.
- What does closing line value tell me?: what beating the closing price shows, and what it cannot.
Every answer on these pages is market data and education. OpenSlate does not publish free picks and does not tell you what to bet; it shows prices and measurements.
More: Removing the vig: how to turn two prices into a fair probability · Why Pinnacle is the reference price · Closing line value, explained · Why parlays cost more than the same bets straight · Why player prop lines move · Is DraftKings or Pinnacle sharper on NBA player props? · How do I calculate a no-vig price? · Why do DraftKings and Pinnacle prop lines differ? · What is a Trap Over? · Are NBA rebound unders profitable? · How do I compare sportsbook prop odds for free? · What does closing line value tell me? · How often do prop lines move before tip-off? · What is the vig on DraftKings player props? · How do injury reports move NBA prop lines? · What is a market-maker sportsbook? · Is it better to bet the over or the under on player props? · Can you make money betting player props? · Can you bet at Pinnacle from the US? · What free tools help with player prop betting? · Does betting DraftKings when it disagrees with Pinnacle work? · What does over/under mean on a player prop? · How do sportsbooks set player prop lines? · What is a sharp bettor? · How do I convert American odds to implied probability? · What is a steam move in sports betting? · What are alternate lines on player props?
Education only, not betting advice. 21+. Problem gambling? Call 1-800-GAMBLER.