Implied Probability
The win probability implied by a set of odds, including the sportsbook's margin.
Implied probability is the chance of winning that a set of odds suggests. Every price a sportsbook posts can be turned into a percentage, and that percentage is the key to deciding whether a bet is worth making.
If you think something will happen more often than its implied probability, the bet has value. If you think it will happen less often, it doesn't.
How to Convert Odds to Implied Probability
- Negative American odds: |odds| / (|odds| + 100) × 100
- Example: -150 → 150 / 250 = 60%
- Positive American odds: 100 / (odds + 100) × 100
- Example: +130 → 100 / 230 = 43.5%
- Decimal odds: 1 / decimal odds × 100
- Example: 1.80 → 1 / 1.80 = 55.6%
- Fractional odds: denominator / (numerator + denominator) × 100
- Example: 5/2 → 2 / 7 = 28.6%
Our Odds Converter does every one of these instantly.
Quick Reference Table
| Favorite | Implied | Underdog | Implied |
|---|---|---|---|
| -500 | 83.3% | +500 | 16.7% |
| -300 | 75.0% | +300 | 25.0% |
| -200 | 66.7% | +200 | 33.3% |
| -150 | 60.0% | +150 | 40.0% |
| -130 | 56.5% | +130 | 43.5% |
| -110 | 52.4% | +110 | 47.6% |
| -100 | 50.0% | +100 | 50.0% |
Why the Two Sides Add Up to More Than 100%
Add the implied probabilities of both sides of a bet and you will almost always get more than 100%. That extra is the sportsbook's margin, also called the overround or vig.
Team A -150 = 60.0% | Team B +130 = 43.5%
60.0% + 43.5% = 103.5%
To get the fair probability, divide each side by the total: 60.0 / 103.5 = 58.0% and 43.5 / 103.5 = 42.0%. Those no-vig numbers are the closest thing to the market's honest estimate.
Implied Probability vs. True Probability
Implied probability is the book's price, not the truth. The whole point of betting well is finding prices where the implied probability is lower than the real chance.
Example: an underdog is +150, which implies 40%. You estimate it actually wins 45% of the time.
Expected value = (0.45 × $1.50) − (0.55 × $1.00) = +$0.125 per $1 bet
That is a 12.5% edge. If your estimate is right, you profit over many bets like it, even though you will still lose this particular bet more often than you win it.
Implied Probability as Your Breakeven Rate
The implied probability of the price you take is also the win rate you need to break even. At -110 you need 52.4%. At -200 you need 66.7%. A bettor who wins 58% of their bets can still lose money if most of those bets are -200 favorites.
Implied Probability in Parlays
For a parlay, multiply the legs' implied probabilities (as decimals). Two -110 legs: 0.524 × 0.524 = 27.4%. Because each leg already includes the book's margin, that margin compounds as you add legs.
Common Mistakes
- Confusing "likely" with "good value." A 75% favorite at -400 (80% implied) is a bad bet.
- Forgetting the vig. Your estimate should beat the no-vig probability, not just the posted one.
- Trusting small samples. Ten wins in a row doesn't prove your estimates are right.
Go deeper with our guide: Understanding Implied Probability.
Key Takeaways
- Implied probability converts odds into a percentage chance of winning.
- Always compare implied probability to your own estimated probability to assess value.
- The sum of all implied probabilities in a market exceeds 100% due to the vig.
Examples
- -110: 52.38% implied probability.
- +200: 33.33% implied probability.
- Even money (-100/+100): 50% implied probability.
Related Terms
Test Your Knowledge
1 / 3Do you know what Expected Value (EV) means?
The average outcome of a bet over time. Positive EV bets profit in the long run.
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Frequently Asked Questions
How do I convert decimal odds to implied probability?
Divide 1 by the decimal odds. Odds of 2.50 imply 1 / 2.50 = 40%.
Why do both sides add up to more than 100%?
The extra is the sportsbook's margin. Two sides at -110 each imply 52.4%, which totals 104.8%. Remove that margin and you get the fair, no-vig probability.