Fractional, decimal, American, implied probability — odds come in confusing formats. Our free betting odds converter instantly translates between all four and shows the true implied probability, so you always know exactly what a price means.
Betting Odds Converter
Convert between fractional, decimal, American odds and implied probability instantly.
Implied probability includes the bookmaker's margin, so the true chance is a little lower. Edit any field to update the rest.
The four odds formats explained
- Fractional (5/2) – traditional UK format. The profit relative to your stake: 5/2 returns £5 profit for every £2 staked.
- Decimal (3.50) – the total return per £1 staked, including your stake. Popular across Europe and on betting exchanges.
- American (+250 / -150) – a positive number shows profit on a £100 stake; a negative number shows the stake needed to win £100.
- Implied probability (28.57%) – the chance of the outcome that the odds represent.
Why implied probability matters most
Converting odds into a percentage is the single most useful skill for a sharp punter. It tells you the bookmaker’s estimated likelihood of an outcome — and lets you judge whether you think the real chance is higher (a value bet) or lower. Remember that a bookmaker’s margin (“overround”) is baked in, so the combined implied probabilities of all outcomes add up to more than 100%. The true chance is always a little lower than the headline figure.
Quick conversion reference
- Decimal → implied %: 100 ÷ decimal odds.
- Fractional → decimal: (numerator ÷ denominator) + 1.
- Decimal → American: if 2.00+, (decimal − 1) × 100; if under 2.00, −100 ÷ (decimal − 1).
Comparing casino value instead of sportsbook prices? Try our Bankroll & Session Calculator to estimate your expected cost of play.
18+. Odds reflect probability, not certainty. Gamble responsibly: BeGambleAware.org.
