The implied probability formula for every odds format
| Odds format | Formula | Example |
|---|---|---|
| American minus | odds / (odds + 100) | -150: 150 / 250 = 60% |
| American plus | 100 / (odds + 100) | +150: 100 / 250 = 40% |
| Decimal | 1 / decimal | 2.50: 1 / 2.50 = 40% |
| Fractional a/b | b / (a + b) | 3/2: 2 / 5 = 40% |
For minus odds, use the number without its sign. The answer is the share of the time a bet at that price has to win for you to break even over many bets, before the vig is taken out. Decimal odds are the quickest to read, since the implied chance is simply one divided by the price. Fractional odds, common in Britain, Ireland and on futures boards, convert just as easily: 5/1 implies 1 / 6, or 16.7 percent. If you prefer not to do the math, the odds converter turns odds to implied probability for any price in one step.
You will also hear implied odds in betting used for the same idea: the chance a price implies. In poker, implied odds means something different (money you expect to win later in a hand), so in sports betting, implied probability is the clearer term.
Implied probability at common prices
| Price | Decimal | Implied probability |
|---|---|---|
| -200 | 1.50 | 66.7% |
| -110 | 1.909 | 52.4% |
| +100 | 2.00 | 50.0% |
| +150 | 2.50 | 40.0% |
| +300 | 4.00 | 25.0% |
| +1000 | 11.00 | 9.1% |
The pattern is worth memorizing. The bigger the minus number, the closer to certain the price says the favorite is. The bigger the plus number, the less often the underdog has to win for the bet to pay its way. If the plus and minus signs are new to you, start there.
Real prices from October 13, 2026
On October 13, 2026, the Odds Screen snapshot at 7:37 PM ET priced the Chicago Bears at Atlanta at -180 at two sportsbooks (Bally Bet and BetRivers) and -155 at theScore Bet. Same team, same game, same moment:
- -180 implies 180 / 280 = 64.3%
- -155 implies 155 / 255 = 60.8%
- -150, the price at the exchanges Novig and ProphetX, implies 60.0%
Betting the Bears at -180 asks you to believe they win more than 64 percent of the time just to break even. At -150 the bar is 60 percent. Four points of implied probability on the same bet is a big gap, and it costs nothing to close it except checking more than one book. That habit is line shopping.
Implied probability also explains line movement. When a favorite moves from -150 to -170, its implied chance climbs from 60.0 to 63.0 percent: either the market now rates that team higher, or the book wants less money on it. Watching the implied chance instead of the raw number makes moves comparable across favorites, underdogs and sports.
Why both sides add up to more than 100 percent
Add the implied probabilities of both sides and the total is almost always above 100 percent. In the same snapshot, FanDuel had Seattle at Denver at -146 and +124: 59.35% + 44.64% = 103.99%. The extra 3.99 percent is the book's margin, also called the overround or the vig.
Divide each side by the total and you remove that margin, which gives the no-vig fair odds. Implied probability with the vig in is the price you pay. Implied probability with the vig out is the market's fair estimate. Keep the two apart and most betting math gets simpler.
Implied probability vs your own estimate
Implied probability is a break-even line, not a prediction. A bet makes sense only when your honest estimate of the chance is higher than the price implies. If you think an underdog wins 45 percent of the time and the price is +150 (40 percent implied), the price pays more than your estimate says it should, so the bet has positive expected value on your numbers.
The hard part is the estimate. Most bettors overrate their own reads. A safer starting point is to treat the no-vig market price as the fair chance and only bet prices that beat it. Sizing should follow the size of the gap, which is what the Kelly criterion formalizes.
Break-even rates and parlays
Implied probability is also your break-even win rate. At -110 you need to win 52.4 percent of your bets to break even, not 50 percent, because of the vig. At +200 you need just 33.3 percent.
For a parlay, multiply the legs. Two legs at -110 imply 52.4% x 52.4% = 27.4% for the ticket, and a book paying about +264 on that parlay implies 27.4% too, so the vig compounds with every leg. Same-game parlays break this rule, because the legs are linked; see same game parlay. How payouts follow from the same numbers is on how betting payouts are calculated.
Common mistakes
- Treating implied probability as a forecast. It is what the price charges, not what will happen.
- Forgetting the vig. Comparing your estimate with a vig-loaded number makes every bet look worse than it is, and comparing it with nothing makes every bet look better.
- Mixing formats. 2.50 decimal and +150 American are the same price. Convert before you compare.
- Reading a stale quote. A price that has not updated is not a price you can bet. Our boards date every quote, and the rules for trusting one are on how we test our tools.
Your next step
Frequently asked questions
How do you calculate implied probability from American odds?
For minus odds, divide the odds by the odds plus 100, so -150 is 150 divided by 250, or 60 percent. For plus odds, divide 100 by the odds plus 100, so +150 is 100 divided by 250, or 40 percent.
What does an implied probability of 60 percent mean?
It means the price only breaks even if the bet wins 60 percent of the time over many tries. If you think the real chance is higher, the price may be worth taking; if lower, it is not.
Why do implied probabilities add up to more than 100 percent?
Because the sportsbook builds its margin into both sides. The amount over 100 percent is the vig. Divide each side by the total to get the no-vig fair probabilities.
Is implied probability the same as the chance a team wins?
No. Implied probability is what the price charges. The chance a team wins is unknown; the no-vig market price is a good estimate of it, but still only an estimate.
Your next step
- 1Learn itImplied Probability (this page)
- 2Apply itHow to read betting odds →
- 3Run itOdds Converter →
- 4Master itDay 2: How sportsbooks make money →
Related terms
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