American odds answer one of two questions. Negative numbers: how much must I risk to win $100? Positive numbers: how much do I win if I risk $100? So -150 means risk $150 to win $100, and +150 means risk $100 to win $150.
The conversion that matters
Every price implies a probability:
| Price | Implied probability |
|---|---|
| -200 | 66.7% |
| -110 | 52.4% |
| +100 | 50.0% |
| +150 | 40.0% |
| +300 | 25.0% |
Negative odds: odds ÷ (odds + 100). Positive: 100 ÷ (odds + 100). The implied probability is also your break-even win rate — at -110 you must win 52.4% of the time just to tread water, which is the book's hold working on you.
Favorites, dogs, and the trap in each
The favorite's trap is juice: -300 wins often and pays little, and one loss erases three wins. The underdog's trap is romance: +400 feels like a lottery ticket, but the only question is whether the true chance beats the 20% the price implies.
The habit
Before any bet, say the implied probability out loud and ask whether you honestly believe the true chance is higher. If you can't answer, that's the answer. This one habit is most of the distance between betting on feelings and betting on numbers — the rest is covered in the [+EV guide](/learn/what-is-expected-value).
