Sports betting odds can look confusing if you've never placed a bet before — especially with three different formats used globally. But once you understand the basic logic, reading odds becomes second nature. This guide explains American, Decimal, and Fractional odds with simple examples, so you can read any bet slip with confidence.
The Three Odds Formats
There are three major odds formats used around the world. US sportsbooks use American odds by default, but most major platforms let you switch to decimal or fractional in your settings.
| Format | Example | Used In | Best For |
|---|---|---|---|
| American (Moneyline) | -110 or +150 | USA | Standard US sports betting |
| Decimal | 1.91 or 2.50 | Europe, Canada, Australia | Parlay calculations |
| Fractional | 10/11 or 3/2 | UK, Ireland | Horse racing, traditional betting |
How to Read American Odds (+/-)
American odds use a + or - sign followed by a number. The sign tells you whether this is an underdog (+) or a favorite (-). The number tells you either how much you win on $100 bet (positive odds) or how much you need to bet to win $100 (negative odds).
Positive American Odds (+) — Underdogs
Positive odds show your profit on a $100 bet. Examples: +150 means a $100 bet wins $150 profit (total return $250). +300 means a $100 bet wins $300 profit (total return $400). +500 means a $100 bet wins $500 profit (total return $600). The higher the + number, the bigger the underdog — and the bigger the payout.
Negative American Odds (-) — Favorites
Negative odds show how much you must bet to win $100 profit. Examples: -110 means bet $110 to win $100 profit (total $210). -200 means bet $200 to win $100 profit (total $300). -400 means bet $400 to win $100 profit (total $500). The higher the - number, the bigger the favorite — and the less you win relative to your stake.
| American Odds | Type | $100 Bet Profit | $100 Bet Total Return | Implied Probability |
|---|---|---|---|---|
| -400 | Heavy favorite | $25 | $125 | 80.0% |
| -200 | Strong favorite | $50 | $150 | 66.7% |
| -110 | Slight favorite / standard vig | $90.91 | $190.91 | 52.4% |
| +100 | Even money | $100 | $200 | 50.0% |
| +150 | Slight underdog | $150 | $250 | 40.0% |
| +300 | Big underdog | $300 | $400 | 25.0% |
| +500 | Heavy underdog | $500 | $600 | 16.7% |
How to Read Decimal Odds
Decimal odds show your total return per $1 staked — including your original bet. They are the easiest format for calculating parlays. Decimal 2.50 means a $1 bet returns $2.50 total. Decimal 1.50 means a $1 bet returns $1.50 total.
- To calculate profit: (Decimal odds − 1) × stake
- To calculate total return: Decimal odds × stake
- Decimal odds below 2.00 = favorites (you win less than you bet)
- Decimal odds above 2.00 = underdogs (you win more than you bet)
- Decimal 2.00 = even money (+100 American)
How to Read Fractional Odds
Fractional odds show profit relative to stake as a fraction. 3/2 means for every $2 you bet, you win $3 profit. 11/10 means for every $10 you bet, you win $11 profit. Fractional odds are the traditional UK format used in horse racing.
- To calculate profit: (numerator / denominator) × stake
- To calculate total return: profit + stake
- Fractions greater than 1 (e.g., 3/1, 5/2) = underdogs
- Fractions less than 1 (e.g., 1/2, 1/4) = favorites
What Is Implied Probability?
Implied probability is the win percentage that a set of odds implies. It tells you how often the sportsbook thinks each side will win. If a team is -200, the implied probability of them winning is 66.7% — the book thinks they'll win two out of every three games.
Here's how to calculate implied probability from American odds:
The key insight: implied probability from the sportsbook's odds always adds up to more than 100% (usually 104–110%). That excess is the vig — the book's built-in profit margin.
Point Spreads vs Moneylines vs Totals
There are three main bet types on every game, each displayed with odds:
- Point Spread: Team A -6.5 (-110) vs Team B +6.5 (-110). Team A must win by 7 or more; Team B can lose by up to 6 and still cover. Both sides typically offered at -110.
- Moneyline: Team A -220 vs Team B +180. Straight up winner, no spread. Bigger payouts on underdogs.
- Total (Over/Under): Over 47.5 (-110) / Under 47.5 (-110). You bet whether the combined final score will be over or under the number. Usually -110 both sides.
Use our free Odds Converter to convert any odds between American, Decimal, and Fractional formats instantly — and check the implied probability.