EV calculator
Enter the price you can bet and how often it should win: as a percentage, as a fair price, or as both sides of a sharp book's line. See what the bet is worth per $100 and the win chance it needs to break even.
The price at the book you would bet with
Same side and line, at a sharp book such as Pinnacle
With the margin removed, this side wins 41.60% (+140)
What you would bet
- EV per $100
- +$1.92Win $145.00 41.60% of the time, lose $100 the rest. Averaged over many bets, this is what each $100 earns.
- EV as a share of the stake
- +1.92%Positive: the price pays more than the win chance is worth.
- EV on a $100 stake
- +$1.92Any one bet still wins $145.00 or loses $100.00. The EV shows up only across many bets.
- Break-even win chance
- 40.82%The price has to win this often to pay its way. Your 41.60% chance (fair price +140) is 0.79 points above it.
What expected value means
Expected value, or EV, is what a bet earns on average if you could place it over and over. For a bet at decimal odds d that wins with probability p, the expected profit per dollar is p × d − 1. Times 100, that is the EV per $100. The break-even win chance is 1 ÷ d: a bet is worth taking only when its real chance of winning is higher.
A worked example
A sharp book prices a moneyline at -150 on the favorite and +130 on the underdog. Implied, that is 60.00% and 43.48%, 103.48% in total. Take the margin out (the power method the no-vig calculator explains) and the underdog's fair chance is 41.60%, a fair price of +140.
Another book offers the underdog at +145, or 2.45. EV = 0.41602 × 2.45 − 1 = +1.92%, or +$1.92 per $100: you win $145 with a 41.60% chance (worth +$60.32) and lose $100 with a 58.40% chance (−$58.40). The price breaks even at 40.82%, so the fair chance clears it by 0.79 points. These are the calculator's starting numbers.
Where the win chance comes from
The answer is only as good as p. A sportsbook's own price includes its margin, so the implied chance on the bet you want is the wrong yardstick. The better one is a sharp book's line with the margin taken out, which is what the no-vig calculator does and what the sharp line option here does for you.
ArbWins's +EV board works the same way at scale. It takes Pinnacle's line on each market, removes the margin the same way, and lists the Arizona prices longer than that fair price, with each one's EV and win chance beside it.
What EV does not tell you
A +EV bet still loses often: the +145 example loses 58% of the time. The edge shows up across hundreds of bets, and only if the fair chance is close to right. Size each bet so a losing run cannot sink the bankroll; the Kelly calculator turns the same price and win chance into a stake.