Parlay calculator & odds converter
Convert odds between American, decimal, fractional and implied probability — then build a parlay to see combined odds and payout.
How betting odds work
American odds (moneyline) show how much you profit on a $100 bet. Negative odds (e.g. -110) mean you must risk that amount to win $100 — so -110 means risk $110 to profit $100. Positive odds (e.g. +150) mean a $100 bet wins $150 profit.
Decimal odds represent total return per $1 wagered including your stake. Decimal 1.91 × $100 stake = $191 total back ($91 profit). Fractional odds (common in UK) express profit relative to stake: 10/11 means win $10 for every $11 wagered. Implied probability converts any odds format into the bookmaker's implied win percentage — a -110 line implies 52.4% chance, which is why books profit over time (the "vig" or "juice").
A parlay combines multiple independent bets. All legs must win for the parlay to pay. The combined decimal odds = product of all individual decimal odds. Parlays offer larger payouts but much lower implied probability — a 4-leg parlay where each leg is 50% implies only 6.25% true probability of winning.