Expected value, in one screen.
Enter your win probability, the American odds on offer, and a stake. The calculator returns the expected value of the play in dollars and as a percentage of your stake. It works instantly on any sport, from an NFL spread to an NBA prop, and it needs no sign-up.
Expected value
Profit if it wins
Risk if it loses
Weighing what you win against what you risk
Expected value answers a single question: if you could place the same wager over and over, what would the average result be? It balances the profit you collect when the play hits against the stake you lose when it misses, weighted by how often you think each happens.
The formula is short. Expected value equals your win probability times the profit on a win, minus your loss probability times the stake you risk. American odds set the profit side, because a positive price pays more than your stake while a negative price pays less, and your probability estimate sets the weighting. A positive answer means the price beats your fair estimate, and a negative answer means it does not.
A concrete walk-through
Say an NFL team is offered at -110 to cover the spread, you judge that outcome a 54% chance, and you are working with a $100 stake. First convert the odds, because -110 in American terms is decimal 1.909, so a winning $100 stake returns about $90.91 in profit.
Now weigh the two sides. On the win side, 54% of the time you collect roughly $90.91. On the loss side, 46% of the time you give back the $100 stake. Multiply and subtract: about $49.09 minus $46.00 leaves an expected value near +$3.09, or a bit over three percent of the stake. Because the number is positive, the -110 price is a touch generous for a 54% estimate. Nudge the probability down to 50% and the same price flips negative, which is why the probability you enter matters as much as the odds. The same arithmetic applies to an NBA points prop or an MLB moneyline, since the math does not care which sport the price came from.
Expected value, answered
What is expected value in betting?
Expected value, or EV, is the average result you would get from a wager if you could place it many times over. It weighs the amount you win when it hits against the amount you lose when it misses, using your estimate of how often each happens. A positive EV means the price is better than your probability implies; a negative EV means it is worse.
How is expected value calculated?
Multiply your win probability by the profit you collect on a win, then subtract your loss probability multiplied by the stake you risk. In short: EV = (win probability × profit if it wins) − (loss probability × stake). The calculator does this for you once you enter a probability, the American odds, and a stake.
What is a good expected value?
Any positive expected value means the odds are priced in your favor relative to your probability estimate. The larger the positive number (shown here both in dollars and as a percentage of stake) the more the price beats your fair estimate. The result is only as reliable as the probability you feed in, so the input matters as much as the output.
Where does the win probability come from?
That is the one number the calculator cannot supply. It is your own estimate of how likely the outcome is. You might derive it from a model, from removing the vig on a two-sided market with our no-vig calculator, or from your own read of the matchup. The EV figure is a direct consequence of that estimate.
Does a positive EV guarantee a profit?
No. Expected value is a long-run average, not a promise about any single result. A positive-EV wager can still lose, and a negative-EV wager can still win. It is an informational estimate meant to describe pricing over many plays, not a prediction of one outcome.
What is the difference between EV in dollars and EV percent?
The dollar figure is the average gain or loss for the exact stake you entered. The percentage restates that same result as a share of the stake, so you can compare plays of different sizes on equal footing. Both describe the same edge from different angles.
From math to model edges
The calculator handles the arithmetic. MySpariEdge does the harder part: estimating the probabilities, with daily model projections shown next to the market price across every board.