Every price carries a win chance: the chance at which the bet breaks even over time. That is the price's implied probability. Comparing it with your own estimate is the core of every betting decision.
Working it out
- From decimal odds: implied probability = 1 ÷ decimal. Decimal 2.50 is 40%.
- A minus American price: the price ÷ (the price + 100), without the sign. −150 is 150 ÷ 250 = 60%.
- A plus American price: 100 ÷ (the price + 100). +130 is 100 ÷ 230 = 43.48%.
| American | Implied probability |
|---|---|
| −220 | 68.75% |
| −150 | 60.00% |
| −110 | 52.38% |
| +130 | 43.48% |
| +150 | 40.00% |
| +200 | 33.33% |
Break-even
The implied probability is your break-even win rate at that price. A bettor laying −110 on every pick has to win 52.38% of them just to stay level, not 50%. The gap is the bookmaker's margin (see the vig guide).
Vig included
Add up the implied probabilities of every outcome in one market and the total comes to more than 100%. At −110 on both sides of a spread, each side implies 52.38%, together 104.76%. So a single price's implied probability overstates its true chance a little. To compare a price with your estimate, compare against the no-vig chance as well: the market's view with the margin taken out.
In Unitley
calc_implied_probability turns American odds into decimal odds and the implied probability, vig included. calc_no_vig_odds takes every price in a market and returns each outcome's fair chance.
Names set like this are Unitley’s tools: what your AI agent, or the analyst in the web app, calls to get these numbers. See the docs