Free online betting odds calculator. Convert between decimal, fractional, and American odds. Calculate potential payouts, implied probability, and parlay odds instantly. Pure client-side, no ads.
This betting odds calculator helps you understand and convert between different odds formats used worldwide. Whether you are betting with decimal odds (popular in Europe and Asia), fractional odds (common in the UK), or American odds (used in the US), our calculator converts them instantly. It also calculates implied probability — the bookmaker's estimated chance of an outcome — and helps you evaluate whether a bet has value. All calculations happen in your browser with no data sent to any server.
Decimal odds (also called European odds) represent the total amount you will receive for every $1 wagered, including your stake. For example, odds of 2.50 mean a $100 bet returns $250 total ($150 profit + $100 stake). They are popular in Europe, Australia, and Canada.
Fractional odds (also called UK odds) show the profit relative to your stake. For example, 5/2 means you win $5 profit for every $2 staked. A $10 bet at 5/2 returns $35 total ($25 profit + $10 stake). They are traditional in the UK and Ireland.
American odds (also called moneyline odds) use a baseline of $100. Positive numbers (+150) show how much profit you make on a $100 bet. Negative numbers (-200) show how much you need to bet to win $100. They are standard in the United States.
Implied probability is the bookmaker's estimated chance of an outcome, derived from the odds. For decimal odds, it is calculated as 1 ÷ decimal odds × 100%. For example, odds of 2.00 imply a 50% chance. If you believe the true probability is higher, the bet may have value.
A parlay (also called an accumulator) combines multiple bets into one. The odds multiply together: if you combine bets at 2.00, 1.50, and 3.00, the combined odds are 2.00 × 1.50 × 3.00 = 9.00. All selections must win for the parlay to pay out. Our calculator handles the math instantly.