Gambling Odds Calculator
18+ · Gambling can be addictive. The house edge means you lose over time.
- House edge
- 2.703%
- Return to player 97.297%
- Expected value per bet
- -$0.27
- Win $10.00 or lose $10.00
- Expected result, 100 bets
- -$27.03
- On $1,000.00 wagered
- Ahead after 100
- 35.53%
- Exactly even: 7.67%
- Fair payout for this chance
- 2.056x
- +105.56 American
- Break-even chance at this payout
- 50.000%
- Your chance: 48.649%
On average you lose $0.2703 of every $10.00 bet. Over 100 bets, one standard deviation of luck is $99.96, so short runs can go either way, but the edge wins as the number of bets grows.
Odds converter
Any price in decimal, American, fractional and implied probability.
- Decimal
- 1.909
- American
- -110
- Fractional
- 10/11
- Implied chance
- 52.38%
How to use it
- Pick an example or enter your own chance: as a percent (48.65), a fraction (18/37) or 1 in N.
- Enter the payout. In decimal it's the total you get back per $1, stake included (2x for even money).
- Enter your stake per bet and how many bets you plan to make.
- Read the house edge, expected value and expected result. The URL saves your inputs for sharing.
- Use the converter to switch any price between decimal, American, fractional and implied probability.
The formulas
For a bet that wins with chance p and pays d times your stake back (stake included), else loses the stake:
house edge = 1 - p × d
expected value per bet = stake × (p × d - 1)
expected result over n bets = n × stake × (p × d - 1)
fair payout = 1 ÷ p, break-even chance = 1 ÷ d
The chance of being ahead after n bets is exact: with W wins you're up W × d - n stakes, and W follows a binomial distribution, so we add up the probability of every W that leaves you in profit. For bets with more than one paying outcome (a case, a wheel with several multipliers) use the house edge calculator, which takes every outcome.
House edge of common bets
| Bet | Chance | Pays | House edge | Loss per $100 bet | Ahead after 100 |
|---|---|---|---|---|---|
| Roulette red (single zero) | 48.65% | 2x | 2.70% | $2.70 | 35.5% |
| Roulette red (double zero) | 47.37% | 2x | 5.26% | $5.26 | 26.5% |
| Roulette single number (single zero) | 2.70% | 36x | 2.70% | $2.70 | 50.9% |
| Coin flip paying 1.98x | 50.00% | 1.98x | 1.00% | $1.00 | 46.0% |
| Dice: 49.5% chance at 2x | 49.50% | 2x | 1.00% | $1.00 | 42.1% |
| 15-slot wheel, 1 green at 14x | 6.67% | 14x | 6.67% | $6.67 | 35.0% |
Chances come from the layout of each game (a single-zero wheel has 37 pockets, 18 of them red; a double-zero wheel has 38). The coin flip, dice and 15-slot wheel rows are generic examples: check the payout the site you play on actually shows. "Ahead after 100" assumes 100 equal bets. So 100 bets of $1 on red at a single-zero wheel cost $2.70 on average, yet you finish ahead 35.5% of the time: the edge shows up over volume, not in every session.
Odds conversion table
| Decimal | American | Fractional | Implied chance |
|---|---|---|---|
| 1.5 | -200 | 1/2 | 66.67% |
| 1.909 | -110 | 10/11 | 52.38% |
| 2 | +100 | 1/1 | 50.00% |
| 2.5 | +150 | 3/2 | 40.00% |
| 3 | +200 | 2/1 | 33.33% |
| 5 | +400 | 4/1 | 20.00% |
| 11 | +1000 | 10/1 | 9.09% |
What most odds calculators leave out
- They convert odds but never compute the house edge or expected loss, which is the number that tells you what a bet costs.
- They assume sports odds in American format and can't take a casino chance like 18/37 or 1 in 37.
- Worked examples with arithmetic slips: a -110 bet at a 56% chance is worth about +$6.91 per $100, for instance.
- No chance of finishing ahead, so it's hard to see how often a negative bet still wins over a short session.
Where to use it
Compare sites on our crypto casinos and CS2 betting sites lists. Check what a game keeps with the house edge calculator. Set a budget first, and see our responsible gambling page if it stops being fun.
FAQ
- How do you calculate gambling odds?
- You need two numbers: the chance of winning and what a win pays. Multiply them to get the return to player. If a bet wins 18 times in 37 and pays 2x your stake back, the return is 18/37 x 2 = 97.30%, and the house edge is the rest, 2.70%.
- What is the house edge?
- The share of every bet the game keeps on average: 1 - chance x payout. With a 2.70% edge you lose $2.70 per $100 wagered over time. It applies to the total you bet, not to your bankroll, so betting the same money again and again multiplies it.
- What does expected value (EV) mean in gambling?
- The average result of a bet if you could repeat it forever: stake x (chance x payout - 1). Negative EV means you lose on average. Every casino game is negative EV for the player by design.
- How do you convert American odds to decimal?
- For positive odds, decimal = 1 + odds / 100, so +150 is 2.50. For negative odds, decimal = 1 + 100 / |odds|, so -110 is 1.909. Fractional a/b is 1 + a/b, so 3/2 is 2.50. Implied probability is 1 / decimal odds.
- What is the fair payout for a bet?
- 1 / chance. A 1 in 37 shot is fair at 37x total return (36 to 1). Roulette pays 36x for a single number, and that gap between 37 and 36 is the house edge.