Expected Value Calculator
Expected value is the single most important concept in sports betting. Enter the book's odds, your estimate of the true probability, and your stake — and see whether a bet is mathematically worth making.
GamblersGuide Tool
Expected value calculator
Book odds
Odds offered by the sportsbook (e.g. -110, +150)
Your true prob %
Your estimate of the real win chance
Stake ($)
How much you plan to bet
Expected value per bet
+$5.00
on a $100 stake · ROI: +5.00%
You have an edge
Book implied prob
52.4%
What the odds say
Your true prob
55.0%
Your estimate
Your edge
+2.62%
You have the edge
Profit if win
$90.91
on $100 stake
Long-run simulation at this EV
What is expected value?
Expected value (EV) is the average amount you'd win or lose per bet if you made the same wager many times. A +EV bet means the odds are in your favor relative to the true probability — you'd profit long-term. A −EV bet means the book's implied probability exceeds your true estimate — you'd lose money over time. Most bets are −EV. Finding +EV requires knowing something the market doesn't.
How to use this calculator
Enter the book odds — Put in the odds exactly as shown by your sportsbook, in whichever format you prefer (American, decimal, or fractional).
Estimate the true probability — This is the hard part. Your edge comes entirely from this number being more accurate than the book's implied probability. Use your own research, models, or judgment. There's no formula — this is where skill lives.
Read the EV — A positive EV means you have an edge on this bet. A negative EV means the book has the edge. The long-run simulation shows what that edge compounds to over hundreds of bets.
Important caveat — Even a +EV bet loses money sometimes. EV is a long-run concept. Short-term variance is real. Never bet more than you can afford to lose, and never assume a single +EV result proves your probability estimate was right.