American Odds to Implied Probability Calculator

Convert moneyline odds to win percentage instantly

Odds Type

Enter American Odds

Quick Conversions

Conversion Formula & Calculation

American odds, also known as moneyline odds, represent the amount you need to wager or the amount you can win on a $100 bet. Converting these odds to implied probability helps you assess the likelihood of an outcome occurring according to the bookmaker.

Negative Odds Formula

When odds are negative (e.g., -150):

de>Implied Probability = |Odds| / (|Odds| + 100) × 100%

Example: Odds of -150
Implied Probability = 150 / (150 + 100) × 100% = 150 / 250 × 100% = 60%

Positive Odds Formula

When odds are positive (e.g., +200):

de>Implied Probability = 100 / (Odds + 100) × 100%

Example: Odds of +200
Implied Probability = 100 / (200 + 100) × 100% = 100 / 300 × 100% = 33.33%

Step-by-Step Conversion Process

Identify the odds type: Determine whether the American odds are positive (+) or negative (-). Negative odds indicate favorites, while positive odds indicate underdogs.
Extract the numerical value: Take the absolute value of the odds (remove the +/- sign) for calculation purposes.
Apply the appropriate formula: Use the negative odds formula for favorites or the positive odds formula for underdogs.
Calculate the percentage: Perform the division and multiply by 100 to get the implied probability as a percentage.
Interpret the result: Higher percentages indicate higher likelihood according to the bookmaker’s assessment.

Common Odds Conversion Table

American Odds	Implied Probability	Interpretation
-1000	90.91%	Heavy favorite
-500	83.33%	Strong favorite
-300	75.00%	Significant favorite
-200	66.67%	Moderate favorite
-150	60.00%	Mild favorite
-110	52.38%	Slight favorite
+100	50.00%	Even money
+150	40.00%	Mild underdog
+200	33.33%	Moderate underdog
+300	25.00%	Significant underdog
+500	16.67%	Strong underdog
+1000	9.09%	Heavy underdog

Practical Applications in Sports Betting

Value Betting Strategy

Compare the implied probability from bookmaker odds with your own probability assessment. If you believe an outcome has a higher chance of occurring than the implied probability suggests, you may have identified a value bet opportunity.

      Example Scenario: A sportsbook offers +300 odds on a team winning, implying a 25% probability. If your analysis suggests the team has a 35% chance of winning, this represents potential value because your assessment exceeds the bookmaker’s implied probability by 10 percentage points.
    

Bankroll Management

Knowing implied probabilities helps you determine appropriate stake sizes. Many professional bettors use the Kelly Criterion, which requires knowing the true probability versus the implied probability to calculate optimal bet sizing.

Line Shopping

Different sportsbooks may offer varying odds for the same event. Converting all odds to implied probabilities allows you to quickly identify which bookmaker offers the best value for your desired wager.

Vigorish (Vig) Consideration

Bookmakers build a profit margin, called vigorish or vig, into their odds. This means the sum of implied probabilities for all possible outcomes typically exceeds 100%. The excess represents the bookmaker’s theoretical profit margin.

Example: In a two-way market:
Team A: -110 (52.38% implied probability)
Team B: -110 (52.38% implied probability)
Total: 104.76%

The 4.76% difference represents the bookmaker’s vig. True probabilities would sum to exactly 100%.

When making betting decisions, some bettors calculate “no-vig” or “fair” odds by removing this margin to determine true probabilities. This provides a more accurate assessment of actual outcome likelihoods.

Frequently Asked Questions

What do negative American odds mean?

Negative American odds indicate how much you need to wager to win $100. For example, -150 means you must bet $150 to win $100 profit. Negative odds typically represent favorites in sports betting markets.

What do positive American odds mean?

Positive American odds show how much profit you would earn on a $100 wager. For instance, +200 means a $100 bet would return $200 in profit if successful. Positive odds generally represent underdogs.

Why is implied probability important in betting?

Implied probability converts odds into a percentage that represents the bookmaker’s assessment of an outcome’s likelihood. This allows you to compare the bookmaker’s opinion with your own analysis, helping identify potentially profitable betting opportunities where you disagree with the market assessment.

Can implied probability be over 100%?

When considering all possible outcomes in a betting market, the sum of implied probabilities typically exceeds 100% due to the bookmaker’s vigorish. However, individual outcome probabilities always fall between 0% and 100%.

How accurate are implied probabilities?

Implied probabilities reflect the bookmaker’s assessment but include a built-in profit margin. They serve as a market consensus but aren’t necessarily accurate predictions. Successful bettors often find edges by identifying discrepancies between implied and actual probabilities.

What are the most common odds in American sports betting?

The most frequently encountered odds are -110 (52.38% implied probability), which is standard for point spreads and many totals markets. This creates a relatively balanced market where both sides have similar implied probabilities after accounting for the bookmaker’s margin.

How do I convert implied probability back to American odds?

For probabilities above 50%, use: American Odds = -(Probability / (1 – Probability)) × 100. For probabilities below 50%, use: American Odds = ((1 – Probability) / Probability) × 100. This allows you to work backwards from probability to odds.

What is the difference between implied probability and true probability?

Implied probability includes the bookmaker’s profit margin (vig), while true probability represents the actual likelihood without any margin. True probabilities for all outcomes in a market sum to exactly 100%, whereas implied probabilities sum to more than 100%.

References

Cortis, D. (2015). Expected values and variances in bookmaker payouts: A theoretical approach towards setting limits on odds. Journal of Prediction Markets, 9(1), 1-14.
Woodland, L. M., & Woodland, B. M. (1994). Market efficiency and the favorite-longshot bias: The baseball betting market. Journal of Finance, 49(1), 269-279.
Levitt, S. D. (2004). Why are gambling markets organised so differently from financial markets? The Economic Journal, 114(495), 223-246.
Sauer, R. D. (1998). The economics of wagering markets. Journal of Economic Literature, 36(4), 2021-2064.