How to Compare Implied Probability to Fair Odds
The implied probability calculator helps bettors compare the implied probability of a betting market against the actual "fair" probability of that market.
Implied Probability is a percentage derived by converting betting odds that represent the likelihood of an outcome occurring. This percentage factors in the bookmaker's profit margin (vig) as well.
One way to use implied probability is to compare the implied probability of a betting market against the actual "fair" probability of that market—without the juice or vig baked in (using No Vig Price).
If we find that the offered implied probability is lower than the fair probability (based on the no-vig line from Pinnacle), then we've officially located the bet we want to take—a bet with Positive Expected Value!
Obviously, we all want to bet on 'winners' but much more importantly we ONLY want to bet on teams where the implied odds are either lower or accurately represent the chance of that team winning.
The key to locating valuable betting opportunities is finding an actual winning probability that is greater than or equal to the implied winning probability estimated by the sportsbook based on the fair odds.
How to Calculate Implied Probability
Nothing in this world seems to be universal these days, betting odds included. The three formats you'll encounter are American, Decimal, and Fractional.
Since these are three separate odds formats, there are different formulas to convert each into implied probability.
How to Convert Decimal Odds to Implied Probability
Decimal odds are the standard format in most countries and are commonly referred to as European odds. They are the most straightforward and can tell you exactly what your potential winnings would be with just a glance.
The decimal represents the amount of money won for every euro wagered. If the odds are 4.50 and you bet €10, the payout upon a win will be €45.
Formula: (1 / Decimal Odds) × 100
Example: 2.10 decimal odds = (1 / 2.10) × 100 = 47.62% implied probability
How to Convert American Odds to Implied Probability
Converting American odds can be more confusing as it requires two formulas, one for positive odds and one for negative odds.
If the odds are positive (+):
Formula: 100 / (Positive Odds + 100) × 100
Example: +110 odds = 100 / (110 + 100) × 100 = 47.62%
If the odds are negative (-):
Formula: (Negative Odds) / (Negative Odds + 100) × 100
Example: -110 odds = 110 / (110 + 100) × 100 = 52.38%
How to Convert Fractional Odds to Implied Probability
Fractional odds are sometimes referred to as British odds or traditional odds. You typically find these across the UK and Ireland. These odds portray the potential profit should the bet win, quoted as a fraction of the stake.
Formula: Denominator / (Numerator + Denominator) × 100
Example: 11/10 fractional odds = 10 / (11 + 10) × 100 = 47.62%
Using Implied Probability for Value Betting
Understanding implied probability is crucial for finding positive expected value bets.
Step-by-step process:
- Find odds at a soft sportsbook (e.g., Bet365 offers 2.10)
- Calculate implied probability (2.10 = 47.62%)
- Find fair probability from No Vig Price (e.g., 45%)
- Compare: 47.62% implied vs 45% fair
- Since implied is HIGHER than fair, this is a -EV bet (skip it)
When to bet: Implied probability LOWER than fair probability = +EV bet
Finding Value with FairOdds Terminal
This calculator shows you HOW to convert odds and calculate implied probability, but FairOdds Terminal does this automatically across 60+ bookmakers.
The terminal displays the No Vig Price (fair probability) for every market and compares it to bookmaker odds (implied probability) to show only +EV opportunities.
Start your free trial for automated value bet detection.
Implied Probability Calculator FAQ
How do you calculate implied probability?
For decimal odds: (1 / decimal odds) × 100. For American positive odds: 100 / (positive odds + 100) × 100. For American negative odds: (negative odds) / (negative odds + 100) × 100. For fractional odds: denominator / (numerator + denominator) × 100.
What is implied probability in betting?
Implied probability is the likelihood of an outcome occurring based on betting odds. It includes the bookmaker's vig. For example, 2.00 decimal odds = 50% implied probability. To find fair probability, you must remove the vig.
How do you convert decimal odds to probability?
Formula: (1 / decimal odds) × 100. Example: 2.10 decimal odds = (1 / 2.10) × 100 = 47.62% implied probability.
How do you convert American odds to probability?
For positive odds (+110): 100 / (110 + 100) × 100 = 47.62%. For negative odds (-110): 110 / (110 + 100) × 100 = 52.38%. Positive odds use different formula than negative odds.
What is the difference between implied and fair probability?
Implied probability includes the bookmaker's vig. Fair probability is after removing vig using No Vig Price calculations. If implied probability is lower than fair probability, you have a positive EV bet.
Why does implied probability matter?
Implied probability helps you identify value bets. Compare it to fair probability (from sharp books like Pinnacle with vig removed). If the bookmaker's implied probability is lower than the fair probability, you've found positive expected value.