What is Implied Probability in Sports Betting? (With Examples)

Understanding implied probability is one of the most important skills in sports betting. Whether you’re a beginner or an experienced bettor, knowing how to convert odds into implied probability helps you spot value, make smarter bets, and ultimately improve your long-term results.

Implied probability is the percentage chance that a sportsbook assigns to a particular outcome, based on the odds they offer. In simple terms, it tells you how likely the bookmaker thinks an event is to happen.

For example, if a team’s odds to win are +200, the implied probability is 33.3%. This means the sportsbook believes the team has a 33.3% chance of winning.

How to Calculate

American Odds

  • Positive Odds (+):
    Implied Probability = 100 / (Odds + 100) × 100
    Example: +200 → 100 / (200 + 100) = 0.333 = 33.3%

  • Negative Odds (–):
    Implied Probability = |Odds| / (|Odds| + 100) × 100
    Example: –150 → 150 / (150 + 100) = 0.6 = 60%

Decimal Odds

Implied Probability = (1 / Decimal Odds) × 100
Example: 2.50 → (1 / 2.50) × 100 = 40%

Fractional Odds

Implied Probability = Denominator / (Denominator + Numerator) × 100
Example: 8/13 → 13 / (8 + 13) × 100 = 61.9%

Quick Reference Table

Odds Type Example Odds Implied Probability
American (+) +200 33.3%
American (–) –150 60%
Decimal 2.50 40%
Fractional 8/13 61.9%

Why it Matters

1. Spotting Value Bets

If your own research suggests an outcome is more likely than the implied probability, you may have found a “value” or +EV (positive expected value) bet. For example, if you believe a team has a 50% chance to win but the odds imply only 40%, the bet could be profitable in the long run.

2. Understanding the Vig (Sportsbook Margin)

Sportsbooks build in a margin (called the “vig” or “juice”) to ensure a profit. This means the implied probabilities for all possible outcomes often add up to more than 100%.
Example: Two teams both at –110 odds each have an implied probability of 52.4%, totaling 104.8%.

3. Advanced Betting Strategies

Implied probability is useful for more than just moneylines. It helps you:

  • Evaluate parlays and straight bets
  • Compare prop bets and futures
  • Find arbitrage opportunities and live betting value

Real-World Example

Suppose you see the Chicago Bears at +150 to win a game.

  • Implied probability: 100 / (150 + 100) = 40%
    If your analysis gives the Bears a 50% chance, this could be a smart value bet.

Frequently Asked Questions

Why don’t implied probabilities add up to 100%?
Because sportsbooks include a margin (vig) to ensure they make a profit, so the total is usually higher than 100%.

Can implied probability guarantee a win?
No. It’s a tool for making informed decisions, not a guarantee of success.

Should I use implied probability for every bet?
Yes! It’s especially useful for moneylines, parlays, props, and futures.

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