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Odds Calculator

Convert between fractional, decimal and American betting odds and implied probability, and work out the payout.

About the Odds Calculator

UK bookmakers often quote fractional odds (5/2: win 5 for every 2 staked), Europe and Australia use decimal odds (3.5: total return per 1 staked) and the US uses moneyline odds (+250 means a 100 stake wins 250; −150 means you stake 150 to win 100).

Implied probability is 1 ÷ decimal odds. Bookmakers' implied probabilities across all outcomes add up to more than 100%; the excess is their margin.

The formula

Decimal = fractional + 1; probability = 1 ÷ decimal

American +A
decimal = 1 + A ÷ 100
American −A
decimal = 1 + 100 ÷ A

Worked example

Example: Implied probability = 25%

  1. Inputs: I have: Fractional odds (e.g. 5/2); Odds: 3/1; Stake (optional): $20.
  2. Formula: Decimal = fractional + 1; probability = 1 ÷ decimal
  3. Result: Implied probability = 25%
  4. Decimal: 4
  5. Fractional: 3/1
  6. American: +300

Questions people ask

What does evens mean?

1/1, decimal 2.0, American +100: a 50% implied chance.

Is implied probability the real chance?

No; it's the bookmaker's price, which includes their margin.