Calculate expected value, house edge, and win probability for any casino game or sports bet.
Standard published house edges for a single-number/pass-line/basic-strategy bet at typical rules. Real numbers vary by casino, table rules, and (for blackjack) how closely you play basic strategy. Slot edges vary widely by machine and are shown here as a representative average — check your casino for actual RTP where published.
The house always has an edge. Blackjack: ~0.5% edge (best odds in the casino). Roulette: 5.26%. Slots: 2-15%. Sports betting: 4-6% average vig.
A negative expected value means you will lose money over time — it is mathematically guaranteed with enough bets. The calculator above shows you exactly how much.
Set a hard budget before you play. Never chase losses. Gambling should be entertainment, not income.
If gambling is causing problems: National Council on Problem Gambling | 1-800-522-4700
Enter the stake, the total you get back if you win, and the probability you think you have. The page returns the expected value of a single bet, the probability you would need to break even, and what a whole session looks like at those numbers. The odds converter at the bottom translates American and decimal prices so you can check your own figures against a sportsbook's.
Enter the payout as the amount returned, not the profit. A $100 bet at even money returns $200, of which $100 is your stake.
A $100 bet that returns $180 if it wins, with a 48% chance of winning:
| Measure | Value |
|---|---|
| Profit if it wins | $80 |
| Break-even probability | 55.6% |
| Expected value per bet | −$13.60 |
| Over 100 such bets | about −$1,360 on $10,000 wagered |
The break-even number is the whole story. To make this bet fair you would need to win 55.6% of the time; at 48% you lose $13.60 on average every time you place it, whether you win or lose that particular bet. A $180 return on a $100 stake is the odds of a coin flip priced as though it were a favourable one.
Expected value is the average outcome if you repeated the bet an unlimited number of times. It is not what happens tonight. In the example above you either win $80 or lose $100, and neither of those is minus $13.60. The expected value describes the drift, and the drift is what decides whether a session, a season or a habit costs you money.
The house edge is the gap between the true probability and the probability implied by the payout. In this example the payout implies a 55.6% chance while the real chance is 48%, so the edge against you is about 7.6 percentage points. That is large by casino standards: most table games run from under 1% to a few percent, which is why they still separate players from their money slowly rather than quickly.
Volume is the multiplier. A negative expected value with a thousand repetitions is a near-certain loss, and no staking system changes the sign of the number. Martingale doubling feels like it cannot fail and simply converts many small wins into one large loss. If the number is negative, the only bet that improves it is no bet.
The average result per bet if you could place it thousands of times. Negative means the bet loses money over time, however the individual results fall.
No. It is an edge that only shows up over many repetitions, and it assumes your probability estimate is right. Most people overestimate their edge.
For a negative price, divide the number by itself plus 100. For −110 that is 110 ÷ 210, which is 52.4%.
Because every game is priced slightly against the player. The margin is small per bet and certain per thousand bets.
It can show you which bets are worse than others. If you gamble, knowing the cost is the useful part; this page cannot make a negative game positive.
Expected value is probability. The help line is the part that matters if the bets are no longer optional.
Last updated: November 2, 2026. Reviewed by David Liu.