▌ Calculator · implied probability · updated 2026-05-09
Odds into
probability.
In one step.
Every set of odds encodes a probability. At -110, the bookmaker implies you must win 52.38% of identical bets just to break even. At +250, they imply a 28.57% chance. These numbers are not forecasts — they are the book's margin-inflated estimates, baked into prices to guarantee their cut.
Converting odds to implied probability is the first step in comparing your own model against the market. If you believe an outcome is more likely than the implied probability says, you have positive expected value. This calculator does the conversion instantly from any odds format.
Calculator
Live · client-side · zero tracking▌ Odds input
Formula: P = 1 ÷ decimal odds × 100
At -110 → P = 1 ÷ 1.9091 = 52.38%
▌ Implied probability
52.38%
The bookmaker implies this outcome wins 52.38% of the time
American
-110
Decimal
1.909
Fractional
10/11
▌ Derivation · implied probability formula
The probability formula
Decimal odds express total return per unit staked. A $1 bet at 2.50 decimal pays $2.50 if
it wins. The implied probability is the reciprocal: P = 1 / decimal.
At 2.50: P = 1 / 2.50 = 0.40 = 40%.
For American odds: convert to decimal first, then apply the reciprocal. At -110:
decimal = 100/110 + 1 = 1.909, then
P = 1/1.909 = 52.38%.
The vig inflates implied probability above the true probability. For a fair 50/50 coin flip, fair decimal odds are 2.00 and true probability is 50%. A bookmaker offering -110 on both sides sets 52.38% implied probability — 2.38% above reality — and collects this margin on every pair of bets.
Using implied probability for edge detection
Edge = your estimated probability − implied probability. If you estimate 58% but the book
implies 52.38%, edge = 5.62%. Kelly criterion optimal bet size for this position:
f = (p × b − (1 − p)) / b where p = your probability,
b = decimal odds − 1. At p = 0.58, b = 0.909:
f = (0.58 × 0.909 − 0.42) / 0.909 = 0.115 = 11.5% of bankroll.
Strip the vig first with the no-vig calculator to see the market's true consensus before comparing to your model.
▌ Reference
Implied probability quick reference
| American | Decimal | Implied Prob | Type |
|---|---|---|---|
| +500 | 6.00 | 16.67% | Heavy underdog |
| +300 | 4.00 | 25.00% | Underdog |
| +200 | 3.00 | 33.33% | Underdog |
| +100 | 2.00 | 50.00% | Even money |
| −110 | 1.909 | 52.38% | Slight favorite |
| −150 | 1.667 | 60.00% | Moderate favorite |
| −200 | 1.500 | 66.67% | Solid favorite |
| −400 | 1.250 | 80.00% | Heavy favorite |
▌ FAQ
Common questions
What is implied probability in betting?
How do I convert -110 to implied probability?
How do I convert +200 to implied probability?
What is the difference between implied probability and true probability?
How do I use implied probability to find betting edges?
What is the overround and how does it relate to implied probability?
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