Implied Probability Calculator
Convert Betting Odds to Win Probability Instantly
Find value bets by comparing bookmaker odds to your estimates
Implied Probability Results
How to Use This Implied Probability Calculator:
- Enter betting odds in any format (American: -150, Decimal: 2.50, Fractional: 3/2)
- Optionally enter your estimated win probability to check for value
- Click "Calculate Probability" or press Enter to see results instantly
- Compare your estimate to the implied probability to find value bets
What is an Implied Probability Calculator?
An implied probability calculator is a free betting tool that converts sportsbook odds into probability percentages. It shows you the implied probability - what percentage chance the bookmaker gives each outcome based on the odds they're offering. For example, -200 odds equal 66.67% implied probability, meaning the bookmaker thinks there's a 2 in 3 chance of that outcome happening.
Our implied probability calculator handles all formats - American (+150/-110), Decimal (2.50), and Fractional (3/2) - making it essential for finding value bets in NFL, NBA, MLB, and all other sports. Understanding implied probability is crucial for profitable betting, as it helps you identify when your estimated probability exceeds what the odds suggest.
How Does the Implied Probability Calculator Work?
Our calculator uses mathematical formulas to convert any betting odds into their probability percentage. Here's the step-by-step process:
Conversion Formulas
American Odds to Implied Probability
- Negative Odds: Implied Probability = |odds| ÷ (|odds| + 100) × 100
- Positive Odds: Implied Probability = 100 ÷ (odds + 100) × 100
Decimal Odds to Implied Probability
- Formula: Implied Probability = (1 ÷ decimal odds) × 100
- Example: 2.50 decimal odds = (1 ÷ 2.50) × 100 = 40%
Fractional Odds to Implied Probability
- Formula: Implied Probability = denominator ÷ (numerator + denominator) × 100
- Example: 3/2 odds = 2 ÷ (3 + 2) × 100 = 40%
Implied Probability Examples by Sport
NFL Implied Odds Calculator Example
Let's use our implied odds calculator to analyze a typical NFL game with point spread betting:
| Bet Type | Odds | Implied Probability | Your Estimate | Value? |
|---|---|---|---|---|
| Chiefs -3.5 | -110 | 52.38% | 58% | ✓ Yes |
| Bills +3.5 | -110 | 52.38% | 42% | ✗ No |
| Over 48.5 | -115 | 53.49% | 51% | ✗ No |
| Under 48.5 | -105 | 51.22% | 49% | ✗ No |
NBA Moneyline Implied Probability
NBA favorites often have high implied probabilities:
| Team | Moneyline Odds | Implied Probability | True Win % |
|---|---|---|---|
| Lakers | -250 | 71.43% | ~68-70% |
| Clippers | +200 | 33.33% | ~30-32% |
| Total | - | 104.76% | 4.76% Vig |
MLB Underdog Value Example
Finding value with MLB underdogs using implied probability:
| Scenario | Underdog Odds | Implied Prob | Historical Win % | Expected Value |
|---|---|---|---|---|
| Home Dog vs Ace | +180 | 35.71% | 38% | +2.29% |
| Division Rival Dog | +150 | 40.00% | 42% | +2.00% |
| Road Dog vs Lefty | +220 | 31.25% | 29% | -2.25% |
Understanding Bookmaker Margins (Vig)
Bookmakers build in a profit margin by ensuring the implied probabilities of all outcomes exceed 100%. Here's how to calculate it:
Calculating the Vig
Formula: Vig = (Total Implied Probability - 100) ÷ Number of Outcomes
Example with NFL point spread at -110 both sides:
- Team A -110: 52.38% implied probability
- Team B -110: 52.38% implied probability
- Total: 104.76%
- Vig: (104.76 - 100) ÷ 2 = 2.38% per side
Implied Probability Quick Reference Chart
| American Odds | Decimal Odds | Fractional | Implied Probability | Break-even Win % |
|---|---|---|---|---|
| -500 | 1.20 | 1/5 | 83.33% | 5 of 6 |
| -200 | 1.50 | 1/2 | 66.67% | 2 of 3 |
| -150 | 1.67 | 2/3 | 60.00% | 3 of 5 |
| -110 | 1.91 | 10/11 | 52.38% | 11 of 21 |
| +100 | 2.00 | 1/1 | 50.00% | 1 of 2 |
| +150 | 2.50 | 3/2 | 40.00% | 2 of 5 |
| +200 | 3.00 | 2/1 | 33.33% | 1 of 3 |
| +300 | 4.00 | 3/1 | 25.00% | 1 of 4 |
| +500 | 6.00 | 5/1 | 16.67% | 1 of 6 |
How to Use This Calculator for Sports Betting
- Calculate the Implied Probability: Use our calculator to convert the bookmaker's odds to a percentage.
- Estimate True Probability: Use your knowledge, statistics, and analysis to estimate the actual probability.
- Compare the Numbers: If your estimated probability is higher than the implied probability, you've found potential value.
- Account for the Margin: Remember that you need to beat the bookmaker's margin (typically 2-5%) to be profitable long-term.
- Track Your Results: Keep records to see if your probability estimates are accurate over time.
Common Mistakes When Using Implied Probability
Ignoring the Vig
Always remember that bookmaker margins mean you need to win more than the implied probability suggests.
Overestimating Favorites
Public bias often inflates favorite odds, creating value on underdogs.
Not Shopping Lines
Different sportsbooks have different odds, which means different implied probabilities. Compare sportsbooks to find the best value on every bet.
Emotional Estimates
Let data drive your probability estimates, not team loyalty or recent results.
Small Sample Sizes
Don't judge your estimates based on a few bets - you need hundreds to validate accuracy.
Frequently Asked Questions
What is an implied probability calculator?
An implied probability calculator is a free betting tool that converts sportsbook odds into probability percentages. It takes any odds format (American, decimal, or fractional) and shows you the implied probability - the percentage chance the bookmaker assigns to that outcome. This helps identify value bets where your estimated probability exceeds the implied probability.
How do you calculate implied probability from odds?
For American odds: Negative odds: Implied Probability = |odds| / (|odds| + 100). Positive odds: Implied Probability = 100 / (odds + 100). For decimal odds: Implied Probability = 1 / decimal odds. For fractional odds: Implied Probability = denominator / (numerator + denominator).
What does 25% implied probability mean?
A 25% implied probability means the bookmaker believes there's a 1 in 4 chance of that outcome occurring. This equals +300 in American odds, 4.00 in decimal odds, or 3/1 in fractional odds. You would need to win this bet more than 25% of the time to be profitable long-term.
How do I know if a bet has value?
A bet has value when your estimated probability of winning is higher than the implied probability from the odds. For example, if you think a team has a 45% chance to win but the odds imply only 40%, that's a value bet. You need to consistently find these edges to profit long-term.
Why do implied probabilities add up to more than 100%?
Implied probabilities exceed 100% because bookmakers build in a profit margin called the "vig" or "juice." For example, both sides of an NFL spread at -110 have 52.38% implied probability, totaling 104.76%. The extra 4.76% is the bookmaker's edge.
What's the implied probability of -110 odds?
The implied probability of -110 odds is 52.38%. This is the most common odds for point spreads and totals in football and basketball. It means you need to win 52.38% of these bets just to break even after accounting for the bookmaker's margin.
Should I only bet when I find value?
Yes, consistently betting only when you have an edge (positive expected value) is the key to long-term profitability. This means only betting when your estimated probability exceeds the implied probability by enough to overcome the bookmaker's margin. Professional bettors are extremely selective and might only find value in 5-10% of games.
Published by: Robert Wood, Topend Sports, July 2025
Last Updated:
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