Implied probability is the win chance a price suggests. It turns odds, which are hard to compare, into percentages, which are easy. It is also the first step in every value calculation in betting.
The formulas
American odds
- Negative: |odds| ÷ (|odds| + 100). −160 → 160/260 = 61.5%
- Positive: 100 ÷ (odds + 100). +160 → 100/260 = 38.5%
Decimal odds
- 1 ÷ decimal. 2.60 → 38.5%
Fractional odds (A/B)
- B ÷ (A + B). 8/5 → 5/13 = 38.5%
All three describe the same price.
Why the sides add up to more than 100%
Take a game priced at −160 / +140:
- −160 → 61.5%
- +140 → 41.7%
- Total: 103.2%
A real game cannot have a 103.2% chance of producing a winner. The extra 3.2% is the sportsbook's built-in margin, called the overround or vig. (What is vig?.)
So implied probability is not the true probability. It is the true probability plus a share of the book's margin.
From implied to fair probability
To estimate the true chance, remove the margin. The simplest way is to divide each side by the total:
- 61.5% ÷ 1.032 = 59.6%
- 41.7% ÷ 1.032 = 40.4%
These are the "no-vig" or fair probabilities. Do this on a sharp market and you have a strong estimate of the real odds. (How to devig odds · No-vig calculator.)
Using implied probability to find value
The rule: if the true probability is higher than the implied probability of your price, the bet is +EV.
Example: fair probability of a team winning is 45%. Your book offers +135, which implies 42.6%. Because 45% > 42.6%, the bet is +EV. Edge = 0.45 × 2.35 − 1 = +5.75%.
Implied probability and break-even
Implied probability is also your break-even win rate. If you only bet −110, you need to win 52.4% of the time to break even, because that is what −110 implies. (Break-even win percentage.)
Handy reference
| Odds | Implied |
|---|---|
| −250 | 71.4% |
| −175 | 63.6% |
| −130 | 56.5% |
| −110 | 52.4% |
| +110 | 47.6% |
| +130 | 43.5% |
| +175 | 36.4% |
| +250 | 28.6% |
| +400 | 20.0% |
Implied probability for parlays
Multiply the decimal odds of each leg, then take 1 ÷ the result. A three-leg parlay at −110 each: 1.909³ = 6.96, so implied probability is 14.4%. The true chance (if each leg is a fair 50%) is 12.5%, which shows how parlays stack the margin. (Parlay math.)
Frequently asked questions
How do you calculate implied probability from odds?
For negative American odds use |odds| ÷ (|odds| + 100), for positive odds use 100 ÷ (odds + 100), and for decimal odds use 1 ÷ odds.
Is implied probability the real chance of winning?
No. It includes the sportsbook's margin, so it slightly overstates every side's chances. Removing the vig gives a fair estimate.
What is the implied probability of −110?
52.38%. That is also the win rate needed to break even betting at −110.