Odds, Probability & Bankroll
Sports betting odds explained
Sports betting odds are the numerical prices a sportsbook sets for a wager, showing the implied probability of an outcome and the payout you receive if your bet wins.
- Decimal odds
- Total payout per unit stake; 2.00 is an even-money bet.1
- Fractional odds
- Profit relative to stake; 1/1 is an even-money bet.2
- American odds
- Positive numbers show profit on a $100 stake; negative numbers show stake needed for $100 profit. +100 is even money.2
- Implied probability (positive American)
- 100 / (odds + 100)4
- Implied probability (negative American)
- |odds| / (|odds| + 100)4
Key points
- Odds represent the bookmaker's assessment of an event's likelihood and determine your potential return.1
- In fixed-odds betting, the price is locked when you place the wager, so the payout is known in advance.3
- The three standard formats — decimal, fractional and American — all express the same information in different ways.2
- Bookmaker margin (the house edge) is built into the odds, meaning the sum of implied probabilities exceeds 100%.
Common odds formats
| Format | Example | Meaning |
|---|---|---|
| Decimal | 2.00 | You receive $2 for every $1 staked (including stake). |
| Fractional | 1/1 | You win $1 for every $1 staked. |
| American | +100 | You win $100 on a $100 stake. |
Where this term is used
Not the same as
- Betting odds explained football — the same concept applied specifically to football/soccer betting markets, not a different odds concept
Related terms
Odds & probability
Fractional odds to decimal
Shows how to convert fractional odds into decimal format.
Odds & probability
Betting odds spread explained
Explains spread betting odds and how they differ from fixed odds.
Odds & probability
Negative betting odds explained
Covers what negative American odds mean and how to read them.
Odds & probability
Kelly betting
Describes the Kelly criterion for sizing bets based on perceived edge.
Odds & probability
Betting odds to probability
Shows how to convert any odds format into an implied probability percentage.
Odds & probability
Futures betting odds
Explains odds for long-term bets such as season winners or tournament outcomes.
Sources
- Odds en.wikipedia.org Provides the definition of odds and the decimal odds format.
- Sports betting en.wikipedia.org Covers sports betting odds formats and fixed-odds betting.
- Fixed-odds betting en.wikipedia.org Explains fixed-odds betting and how odds are locked at placement.
- Player Props: Understanding the Math Behind the Lines wizardofodds.com Supplies the implied probability formulas for American odds.
Sources are drawn from regulators, universities and published research, and each one is labelled with what it actually is — a preprint is not called a paper. Bookmaker and affiliate pages are never cited here, because a page that sells betting is not a neutral authority on it.