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Odds Converter

Instantly convert between Fractional, Decimal, and American odds formats. Also calculates the Implied Probability (the true winning chance).

Betfair / European
UK Standard
Moneyline (+/-)
True Win Chance

Understanding Betting Odds Formats

If you bet online, you will encounter three main formats. They all represent the same thing (Risk vs Reward), but they look very different.

The 3 Formats Explained

  • Fractional (e.g., 5/2): The UK standard. It shows your Profit relative to your stake.
    Example: Bet £2 to win £5 profit.
  • Decimal (e.g., 3.50): The Exchange/European standard. It shows your Total Return (Profit + Stake).
    Example: Bet £1 to get £3.50 back. (This is usually easier for math).
  • American (e.g., +250): Used in US Sports.
    Positive (+): Profit on a $100 bet. (+250 = Bet $100 to win $250).
    Negative (-): Stake needed to win $100. (-150 = Bet $150 to win $100).

Why is "Implied Probability" important?

The green box in this calculator is arguably the most important number in betting. Bookmaker odds are just a representation of probability.

If a horse is 3/1 (4.0), the market is saying it has a 25% chance of winning.
If you believe the horse actually has a 30% chance, you have found "Value." Knowing this percentage is the first step to using advanced strategies like the Kelly Criterion Read my blog on percenatges.Here.

Tools for Value Hunters

Found a value bet? Use these to maximize it.

Kelly Criterion (Staking) → Arbitrage Calculator → Dutching Calculator →

Disclaimer: Conversions are mathematical approximations. Fractional odds are rounded to the nearest standard industry fraction where possible.