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Implied Probability Calculator

Convert betting odds to probability percentages. Enter American, decimal, or fractional odds to see implied probability, break-even rates, and fair value after removing sportsbook margins. Compare multiple books to find the best lines.

Enter positive odds (+150) for underdogs or negative odds (-150) for favorites
Enter the odds for the opposite outcome to calculate fair odds without vig

Options

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Enter probability as a percentage (e.g., 52.38 for 52.38%)
Based on your analysis, what's the TRUE probability of this outcome?
What odds is the sportsbook offering?
Enter your bet size for EV calculation

Common Betting Odds Conversions

American Odds Implied Probability Decimal Odds Fractional Odds Meaning
-50083.33%1.201/5Heavy favorite
-40080.00%1.251/4Heavy favorite
-30075.00%1.331/3Strong favorite
-20066.67%1.501/2Solid favorite
-15060.00%1.672/3Moderate favorite
-11052.38%1.9110/11Slight favorite
+10050.00%2.001/1Even money
+11047.62%2.1011/10Slight underdog
+15040.00%2.503/2Moderate underdog
+20033.33%3.002/1Solid underdog
+30025.00%4.003/1Strong underdog
+40020.00%5.004/1Heavy underdog
+50016.67%6.005/1Heavy underdog

The Math Behind the Odds

Why This Matters:

Sportsbooks convert probabilities into odds using specific formulas. At -150, the math shows a 60% implied probability, but this includes the book's profit margin. Compare this percentage against the market odds using our Spread to Moneyline Converter to spot any value. When your own probability assessment exceeds the implied probability, you've identified an edge.

Key Concepts:

Overround (Vig)
Sportsbooks set odds so the implied probabilities of all outcomes total more than 100%. The excess represents their profit margin, typically 4-5% for major sports.
Fair Odds
The actual odds after removing the vig. When both sides are -110 (52.38% each), fair odds approach +100 (50% each).
Finding Value
Value exists when your estimated probability exceeds the implied probability, indicating positive expected value (EV).
Break-Even Point
The win rate required to profit at given odds. At -110, you need a 52.38% win rate to break even.

Conversion Formulas

American Odds to Implied Probability

Negative Odds (Favorites):
Probability = |Odds| / (|Odds| + 100)
Example: -150 → 150 / (150 + 100) = 60%
Positive Odds (Underdogs):
Probability = 100 / (Odds + 100)
Example: +200 → 100 / (200 + 100) = 33.33%

American Odds to Fractional Odds

Negative Odds: Fractional = 100 / |Odds|
Example: -150 → 100/150 = 2/3
Positive Odds: Fractional = Odds / 100
Example: +200 → 200/100 = 2/1

American Odds to Decimal Odds

Negative Odds: Decimal = (100 / |Odds|) + 1
Example: -150 → (100 / 150) + 1 = 1.67
Positive Odds: Decimal = (Odds / 100) + 1
Example: +200 → (200 / 100) + 1 = 3.00

Probability to American Odds

If Probability > 50%: Odds = -(Probability / (1 - Probability)) × 100
Example: 60% → -(0.60 / 0.40) × 100 = -150
If Probability < 50%: Odds = ((1 - Probability) / Probability) × 100
Example: 33.33% → ((0.6667) / 0.3333) × 100 = +200

Calculating Expected Value

Expected Value Formula:
EV = (Probability of Winning × Potential Profit) - (Probability of Losing × Stake)
Hypothetical Example Calculation

Example Calculation:

Estimated probability 55%
Market odds +150 (40% implied)
Stake $100
EV = (0.55 × $150) - (0.45 × $100)
EV = $82.50 - $45.00
EV = +$37.50

Positive EV detected. Edge: 15 percentage points (55% estimated vs 40% implied).

EV Percentage:

EV% = ((True Probability × Decimal Odds) - 1) × 100
EV% = ((0.55 × 2.50) - 1) × 100 = +37.5%

Decision Matrix:

EV > 0 Positive expected value
EV = 0 Break even scenario
EV < 0 Negative expected value

Sportsbook Profit Margins & Vig

Example: NFL Game

  • Team A: -110 (52.38% implied)
  • Team B: -110 (52.38% implied)
  • Total: 104.76% (4.76% is the vig)

Fair Odds (No Vig):

  • Each team: 50.00% probability
  • Each team: +100 American odds
  • Each team: 2.00 decimal odds

The 4.76% difference is the sportsbook's profit margin on every $100 wagered.

How to Remove Vig:

  1. Convert both sides to implied probability
  2. Add them together (e.g., 104.76%)
  3. Divide each side by the total
  4. Team A fair probability: 52.38% / 104.76% = 50%
  5. Team B fair probability: 52.38% / 104.76% = 50%

Frequently Asked Questions

What is implied probability?

Implied probability is the conversion of betting odds into a percentage. It represents the likelihood of an outcome as reflected by the sportsbook's odds. For example, -150 odds converts to 60% implied probability, meaning the book prices this outcome as having a 60% chance of occurring.

How do I calculate implied probability from American odds?

For negative odds (favorites), divide the absolute value of the odds by (absolute value + 100), then multiply by 100. For positive odds (underdogs), divide 100 by (odds + 100), then multiply by 100.

Example: -150 becomes 150/(150+100) = 60%
Example: +200 becomes 100/(200+100) = 33.33%

Why is implied probability higher than true probability?

Sportsbooks build a profit margin (vig or juice) into their odds. When you add the implied probabilities of all possible outcomes, the total exceeds 100%. This excess is the book's edge. For example, if both sides of a bet are -110 (52.38% each), the total is 104.76%, with the extra 4.76% representing the sportsbook's profit margin.

What are fair odds after removing vig?

Fair odds represent the true probability after removing the sportsbook's profit margin. Calculate by converting both sides to implied probability, adding them together, then dividing each side by the total. If both sides are -110 (52.38%), the total is 104.76%. Divide each: 52.38/104.76 = 50% fair probability for each side, which converts to +100 (even money) American odds.

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