Implied probability calculator: odds to probability and overround
1win, licensed under Curaçao 8048/JAZ, offers 40,000+ sports markets every day to over 400,000+ registered players. This implied probability calculator converts any odds format into win probability and calculates the overround (margin) built into a full market. Use promo code XLBONUS when you register.
Implied probability and overround calculator
Enter odds for each outcome in your market. Add as many outcomes as needed.
How this calculator works
Every set of betting odds implies a probability. For decimal odds, implied probability = 1 / odds, expressed as a percentage. For a decimal price of 2.50, the implied probability is 40%. For American +200, the conversion is 100 / (200 + 100) = 33.33%.
When you sum the implied probabilities across all outcomes in a market, you get a figure above 100%. This excess is called the overround, vig, or bookmaker margin. A 2-way market where both sides are priced at 1.91 has an overround of (1/1.91 + 1/1.91) - 1 = 4.7%. The bookmaker expects to retain approximately 4.7 cents per dollar wagered across a balanced book.
The fair (no-margin) probability for each outcome can be estimated by dividing the raw implied probability by the sum of all implied probabilities. For example, if Team A has a raw implied probability of 55% and the total overround is 105%, the fair probability for Team A is 55/105 = 52.38%.
Lower overround means better value. A market with 2% overround returns 98 cents per dollar on average; one with 10% overround returns only 90 cents. Comparing overrounds across bookmakers is a quick way to identify which offers the best price on a given market.
The calculator supports any number of outcomes, making it useful for 2-way (match result with no draw), 3-way (home/draw/away), and multi-outcome markets like outright winners. The overround will naturally be higher for markets with more outcomes because each additional pricing decision compounds margin.
This tool is also useful for detecting whether implied probabilities across a full market are consistent (sum to a sensible overround). Wildly inconsistent markets with very high overrounds (above 15%) should raise a red flag about market efficiency or promotional pricing.
Why use it at 1win
1win prices 40,000+ markets with competitive overrounds across football, tennis, basketball and more. Claim code XLBONUS when you register to get started with a boosted balance.
FAQ
What is a good overround for a sports market?
Premier football and tennis markets at competitive bookmakers typically carry 2-5% overround. Markets with 10%+ overround are generally poor value. Anything below 1.5% is exceptional.
How do I calculate implied probability from American odds?
For positive American odds: probability = 100 / (odds + 100). For negative: probability = |odds| / (|odds| + 100). So +150 implies 40% and -200 implies 66.67%.
What is the difference between implied and true probability?
Implied probability is read directly from the bookmaker price and includes the overround. True (fair) probability divides implied probability by the total overround to remove the margin.
Why does implied probability sometimes exceed 100% across a market?
The excess over 100% is the bookmaker's built-in margin. A 2-way market summing to 105% means 5% overround; the book profits by 5% on average across a balanced book.
Can I use this for mga casino game?
Yes. You can enter the odds of any casino outcome to see its implied probability and the house edge (equivalent to overround). For example, a single number in European roulette pays 36:1 (decimal 37.00), implying 2.70% probability against a true 1-in-37 probability of 2.703%.