Odds format conversion formulas
Every format represents the same underlying probability — they're just different conventions used by different markets and regions.
Which odds format should I use?
Decimal odds are the easiest format for arbitrage calculations because the math is simple and intuitive — your total return is always odds × stake. All Australian bookmakers and most European ones use decimal by default.
American (moneyline) odds are standard in the United States. If you're using US-facing sportsbooks like FanDuel, DraftKings, BetMGM or Caesars, you'll need to convert to decimal to run arbitrage calculations accurately.
Fractional odds are the traditional UK format, still used on some UK horse racing and ante-post markets. They show net profit only, which makes cross-book comparison harder than decimal.
Implied probability is the most useful format for evaluating value and arbs — if two bookmakers' implied probabilities for a two-outcome event sum to less than 100%, you have a sure bet.
Frequently asked questions
All major Australian bookmakers — Sportsbet, Ladbrokes, Neds, TAB, Bet365, Unibet, and PointsBet — display decimal odds as standard. This is the same format used across Europe. If you're cross-referencing with US sites or UK racing, you'll need to convert.