Implied Probability Calculator
Enter betting odds in any format - American moneyline (+150, -110), decimal (2.50), or fractional (3/2) - and instantly see the implied probability as a percentage. The calculator also strips the bookmaker margin (vig) from a two-side market to reveal the true fair probabilities, shows you the odds in every other format, and tells you whether a line offers positive expected value given your own probability estimate.
What is implied probability?
Implied probability is the bookmaker's built-in assessment of how likely an outcome is to occur, expressed as a percentage. It is "implied" because it is not stated outright - it is hidden inside the odds. When a sportsbook sets -110 on both sides of a coin-flip market, the implied probability for each side is 52.4%, even though each side should be 50%. That extra 2.4% per side (totalling 4.8% across both) is the bookmaker's margin, also called the vig or juice. Understanding implied probability is the foundation of value betting: if you believe an outcome has a higher probability than the odds imply, the bet has positive expected value.
How to convert odds to implied probability
The conversion formula depends on the odds format. For American odds, negative odds (favourites) use the formula: |odds| / (|odds| + 100). So -150 gives 150 / 250 = 60%. Positive odds (underdogs) use: 100 / (odds + 100). So +200 gives 100 / 300 = 33.3%. For decimal odds, the formula is simply 1 / decimal odds - a decimal of 1.909 gives 1 / 1.909 = 52.4%. For fractional odds, use denominator / (numerator + denominator) - so 10/11 gives 11 / (10 + 11) = 52.4%. All three formats represent the same underlying probability; they are just different conventions used in different markets.
Removing the vig to find fair odds
Because bookmakers price both sides of a market above 100% implied probability in total, comparing two lines directly can mislead you. To find the true, no-vig probability, sum the implied probabilities for both sides of the market to get the overround, then divide each side's implied probability by the overround. For example, if both sides of a market are priced at -110 (52.4% each), the overround is 104.8%. The no-vig probability for each side is 52.4% / 1.048 = 50.0% - reflecting the true coin-flip odds underneath. Fair decimal odds are simply 1 / no-vig probability.
Using implied probability to find value bets
A value bet exists whenever your assessed probability of an outcome is higher than the probability implied by the odds. If you estimate a team has a 55% chance of winning but the odds imply only 50%, you have a 5% edge. Over many bets at that edge, you will profit regardless of short-term variance. The expected value formula makes this precise: EV = P(win) x net profit - P(lose) x stake. A positive EV means that wager is mathematically profitable in the long run. Consistently finding and betting positive-EV lines is the core discipline of professional sports betting.
Common odds and their implied probabilities
| American | Decimal | Fractional | Implied probability |
|---|---|---|---|
| +300 | 4.000 | 3/1 | 25.0% |
| +200 | 3.000 | 2/1 | 33.3% |
| +150 | 2.500 | 3/2 | 40.0% |
| +110 | 2.100 | 11/10 | 47.6% |
| +100 | 2.000 | 1/1 | 50.0% |
| -110 | 1.909 | 10/11 | 52.4% |
| -120 | 1.833 | 5/6 | 54.5% |
| -150 | 1.667 | 2/3 | 60.0% |
| -200 | 1.500 | 1/2 | 66.7% |
| -300 | 1.333 | 1/3 | 75.0% |
Quick reference: standard betting lines converted to win percentages.
Frequently asked questions
What does implied probability mean in betting?
Implied probability is the percentage chance of winning embedded in the betting odds. It is called "implied" because it is derived from the odds rather than stated outright. For example, -110 American odds imply a 52.4% probability of winning. The gap between implied probability and your own probability estimate is your betting edge.
How do I convert American odds to implied probability?
For negative (favourite) American odds, divide the absolute value by (absolute value + 100). Example: -150 gives 150 / 250 = 0.60 = 60%. For positive (underdog) odds, divide 100 by (odds + 100). Example: +200 gives 100 / 300 = 0.333 = 33.3%.
What is the vig (juice) and how does it affect implied probability?
The vig is the bookmaker's profit margin, embedded by pricing both sides of a market above 50% implied probability. A typical -110/-110 market has 52.4% on each side, totalling 104.8% - the extra 4.8% is the vig. This means the implied probabilities you see are always slightly inflated; use the vig-removal feature to find the true fair probability after stripping the margin.
What is a no-vig or fair probability?
Fair (no-vig) probability is the implied probability after removing the bookmaker margin. It is calculated by dividing each side's implied probability by the total overround. If both sides of a market show 52.4% (overround 104.8%), the fair probability is 52.4% / 1.048 = 50.0% for each side, which is the "true" market-neutral probability.
How do I convert decimal or fractional odds to implied probability?
For decimal odds, divide 1 by the decimal. Odds of 2.50 give 1 / 2.50 = 40%. For fractional odds such as 3/2, divide the denominator by the sum of both numbers: 2 / (3 + 2) = 40%. Both give the same result as a +150 American line.
What is the breakeven win rate?
The breakeven win rate is the minimum percentage of bets you must win to avoid losing money at a given set of odds. It is identical to the implied probability. At -110 odds (implied probability 52.4%), you must win at least 52.4% of your bets to break even. Winning more than 52.4% produces profit; winning less produces a loss.
What does expected value (EV) mean in sports betting?
Expected value (EV) is the average profit or loss per bet if you were to place the same wager an infinite number of times. Positive EV means the bet is mathematically profitable given your probability estimate; negative EV means it loses money on average. EV = P(win) x net winnings - P(lose) x stake. For example, at +150 odds with a true 45% win probability: 0.45 x $150 - 0.55 x $100 = $67.50 - $55.00 = +$12.50 per $100 bet.