Expected value calculator
Enter the odds and how often you think the bet wins to see whether the price is worth taking.
Your bet
Expected value of this bet
+10.00At your win chance, this price is better than fair. The result depends on how accurate your estimate is.
What expected value means
Expected value, or EV, is what a bet makes or loses on average if you could repeat it many times at the same price. A positive number means the odds pay more than the risk you are taking. Any single bet still wins or loses in full.
The expected value formula
Multiply your win chance by the profit if it wins, then subtract your chance of losing multiplied by the stake. A shorter version is the win chance times the decimal odds, minus 1, times the stake.
Worked example
You stake 100 at 2.00 and think the bet wins 55% of the time. You expect 0.55 x 100 of profit and 0.45 x 100 of loss, which is an EV of +10, or a 10% edge. At the same 55% and odds of 1.70, the EV drops to about -6.50, so the same opinion is not worth betting at the shorter price.
Where your win chance comes from
The calculator is only as good as the number you give it, and most bettors overrate their picks. A record of your past bets is a good reality check: if you think you win 55% of bets at a certain price but your history says 49%, use 49%. To see what your actual win rate and odds add up to, try the ROI calculator. If you know your number, the Kelly calculator shows the stake it implies.
FAQ
What does +EV mean in betting?
A positive expected value means that, at your estimated win chance, the odds pay more than the bet is worth. Over many similar bets you would expect to profit, if your estimate is right.
How do you calculate expected value?
Multiply your win chance by the decimal odds, subtract 1, then multiply by the stake. A 55% chance at 2.00 with a 100 stake gives (0.55 x 2 - 1) x 100, which is +10.
What is the break-even rate?
It is the win rate that gives an EV of zero at a given price, worked out as 100 divided by the decimal odds. At 2.00 it is 50%, and at 1.91 it is 52.36%.
What are fair odds?
Fair odds are the price with an EV of exactly zero at your win chance, worked out as 1 divided by the chance. A 55% chance has fair odds of 1.82, so anything longer has positive EV by your estimate.
Does a positive EV bet always win?
No. EV describes the average over many bets, and any one bet can still lose. A run of losses is normal, even if your estimates are good.
Are you really beating the price?
Bet Journal records every bet and shows your ROI by odds range, sport and bet type, so you can test your estimates against your real results. Free on iOS and web.