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Player A / Team 1
Player B / Team 2

Reference: Average Bookmaker Margins

BookmakerAvg MarginRating
Pinnacle2.3%Best
Betfair (Exchange)2.5%*Good
Bet3655.1%Avg
Bovada5.8%High
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About

In sports markets, odds represent more than just potential returns; they indicate the Implied Probability of an outcome. For tennis bettors, identifying discrepancies between bookmakers is key to finding value or securing a guaranteed profit through Arbitrage. This tool converts between Decimal, Fractional, and American formats while simultaneously calculating the Bookmaker's Margin (the "Vig"). If the combined implied probability of both players is less than 100%, an arbitrage opportunity exists, and the calculator determines the precise stake distribution required to lock in a profit regardless of the match winner.

betting calculator arbitrage implied probability odds converter surebet

Formulas

The arbitrage condition relies on summing the implied probabilities of all possible outcomes (Player A and Player B). If the sum S is less than 1, the market is inefficient.

S = 1Oa + 1Ob

If S < 1, Profit is guaranteed. The stake for Player A (Stakea) given total investment T is:

Stakea = T × (1 / Oa)S

Reference Data

Odds FormatExampleImplied Prob FormulaConversion to Decimal
Decimal (EU)1.901Oddsx
American (US)-110 / +120Neg: |O||O| + 100Neg: (100/|O|)+1
Fractional (UK)4/5DN + D(N/D)+1
ArbitrageAnyP1 + P2 < 100%N/A

Frequently Asked Questions

Also known as the "vig" or "juice", it is the percentage over 100% that the implied probabilities sum to. A margin of 5% means the bookmaker theoretically keeps $5 of every $105 bet over the long run.
A surebet (arbitrage) occurs when different bookmakers have such different opinions on a match that you can bet on Player A at Bookie X and Player B at Bookie Y, guaranteeing a profit regardless of who wins.
Decimal odds are the mathematical standard for probability. They represent the total payout (Stake + Profit), making calculations for arbitrage and implied probability much cleaner than Fractional or Moneyline formats.