Convert odds between American, decimal, fractional and implied probability — then build a parlay to see combined odds and payout.
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.
For positive American odds: decimal = (American / 100) + 1. For example +150 → (150/100) + 1 = 2.5. For negative American odds: decimal = (100 / |American|) + 1. For example -110 → (100/110) + 1 = 1.909.
Convert each leg to decimal odds, then multiply them all together. A 3-leg parlay with odds 1.91 × 2.50 × 1.75 = 8.354 combined decimal. That means a $100 bet pays $835.40 total ($735.40 profit).
Implied probability is the win percentage implied by the odds. For -110: implied % = 110 / (110 + 100) = 52.38%. For +150: implied % = 100 / (150 + 100) = 40%. If both sides of a bet sum above 100%, the excess is the bookmaker's built-in edge (the vig).
A push means the bet tied (e.g. final score exactly hit the spread). Most sportsbooks treat a push as a "no action" leg — the parlay drops to one fewer leg rather than losing. Always check house rules as they vary by book.