Odds Calculator
Convert betting odds between American, decimal, and fractional formats instantly. Calculate implied probability and potential payouts to make informed betting decisions across all sports and markets.
Understanding Betting Odds Formats
Betting odds represent the probability of an outcome and determine your potential payout. Different regions use different formats - American odds in the United States, decimal odds in Europe and Australia, and fractional odds predominantly in the United Kingdom and Ireland. All three formats convey identical information about likelihood and returns, just expressed differently.
Understanding how to read and convert between these formats empowers you to bet on international sportsbooks, compare value across platforms, and quickly calculate expected returns regardless of how odds are displayed.
American Odds Explained
American odds, also called moneyline odds, center around a $100 benchmark. Positive odds (like +150) indicate how much profit you'd make on a $100 bet. A $100 wager at +150 returns $150 profit plus your $100 stake, totaling $250. Negative odds (like -200) show how much you must bet to profit $100. At -200, you'd risk $200 to win $100 profit, receiving $300 total (your $200 stake returned plus $100 profit).
The sign immediately reveals the favorite versus underdog. Negative odds mark the favorite (higher probability, lower payout), while positive odds signal the underdog (lower probability, higher payout). A matchup showing Team A at -180 and Team B at +160 identifies Team A as the favorite expected to win.
Decimal Odds Explained
Decimal odds represent your total return - both profit and stake - per dollar wagered. Odds of 2.50 mean a $1 bet returns $2.50 total: your $1 stake plus $1.50 profit. This straightforward format makes payout calculations simple: multiply your stake by the decimal odds.
A $50 bet at 3.75 decimal odds returns $50 × 3.75 = $187.50 total. Decimal odds below 2.0 indicate a favorite (you risk more than you can profit), while odds above 2.0 mark an underdog (potential profit exceeds your risk). Odds of exactly 2.0 represent a 50/50 proposition, equivalent to +100 American or 1/1 fractional.
Fractional Odds Explained
Fractional odds display your profit relative to your stake as a ratio. Odds of 3/2 (read "three-to-two") mean you profit $3 for every $2 wagered. A $20 bet at 3/2 calculates as ($20 ÷ 2) × 3 = $30 profit, plus your $20 stake returned, totaling $50.
When the first number exceeds the second (like 5/1), it's an underdog. When the second number is larger (like 1/4), it's a favorite. Traditional horse racing and UK bookmakers favor this format. The fraction 1/1 (even money) equals 2.0 decimal or +100 American, representing equal profit to stake.
| American | Decimal | Fractional | Implied Probability | $100 Bet Returns |
|---|---|---|---|---|
| +100 | 2.00 | 1/1 | 50.00% | $200 ($100 profit) |
| +150 | 2.50 | 3/2 | 40.00% | $250 ($150 profit) |
| +200 | 3.00 | 2/1 | 33.33% | $300 ($200 profit) |
| -110 | 1.91 | 10/11 | 52.38% | $190.91 ($90.91 profit) |
| -200 | 1.50 | 1/2 | 66.67% | $150 ($50 profit) |
How to Calculate Implied Probability from Odds
Implied probability converts odds into a percentage representing the likelihood the sportsbook assigns to an outcome. This calculation reveals the bookmaker's assessment and helps identify valuable bets when your analysis differs from the implied probability.
Converting Decimal Odds to Probability
Decimal odds offer the simplest probability calculation: divide 1 by the decimal odds, then multiply by 100 for a percentage. For 2.50 decimal odds, the math is (1 ÷ 2.50) × 100 = 40%. The sportsbook implies a 40% chance of this outcome occurring. Lower decimal numbers mean higher implied probability - 1.50 decimal converts to 66.67% probability.
Converting American Odds to Probability
American odds require different formulas for positive versus negative values. For positive odds like +150, calculate: 100 ÷ (odds + 100) × 100. That's 100 ÷ (150 + 100) × 100 = 100 ÷ 250 × 100 = 40%. For negative odds like -200, use: (negative odds) ÷ (negative odds + 100) × 100. That's 200 ÷ (200 + 100) × 100 = 200 ÷ 300 × 100 = 66.67%.
Converting Fractional Odds to Probability
For fractional odds, divide the denominator by (numerator + denominator), then multiply by 100. Odds of 3/2 calculate as: 2 ÷ (3 + 2) × 100 = 2 ÷ 5 × 100 = 40%. Odds of 1/4 become: 4 ÷ (1 + 4) × 100 = 4 ÷ 5 × 100 = 80% implied probability, reflecting a heavy favorite.
Finding Value Bets Using Implied Probability
Professional bettors focus on identifying value - situations where their assessment of true probability exceeds the bookmaker's implied probability. If you calculate a team has a 50% chance of winning but the sportsbook's odds imply only 40% (like +150), that represents potential value worth betting.
Understanding the Overround and Vig
Sportsbooks build in a profit margin called "overround," "vig," or "juice." If you add the implied probabilities for all possible outcomes in an event, they'll exceed 100% - often totaling 105-110%. This excess is the bookmaker's edge. A two-outcome bet with each side at -110 (52.38% implied probability) totals 104.76% probability. That 4.76% represents the vig, ensuring the book profits regardless of outcome.
Removing the vig reveals "true" or "fair" odds. Advanced bettors calculate no-vig lines to better assess actual value. You can use our probability calculator for more detailed statistical analysis, or try our poker odds calculator for specific card game probabilities.
Practical Betting Examples with Real Numbers
Let's examine actual betting scenarios to demonstrate how odds translate to payouts and probabilities across different formats.
Example 1: NFL Underdog Bet
You find the Kansas City Chiefs at +175 to win straight up against the Baltimore Ravens. With a $50 stake, let's calculate your potential return. American odds of +175 convert to 2.75 decimal or 7/4 fractional. Your potential profit is ($50 ÷ 100) × 175 = $87.50. Total payout including your stake returned is $137.50. The implied probability is 100 ÷ (175 + 100) = 36.36%. If you believe Kansas City has better than a 36.36% chance, this bet offers value.
Example 2: Tennis Favorite Bet
Rafael Nadal is listed at -250 to defeat an opponent on clay. You want to bet $100. These negative American odds convert to 1.40 decimal or 2/5 fractional. Your potential profit calculates as ($100 ÷ 250) × 100 = $40. With your $100 stake returned, total payout is $140. The implied probability is 250 ÷ (250 + 100) = 71.43%. Nadal must win more than 71.43% of the time long-term for this bet to be profitable.
Remember that odds calculators provide mathematical conversions and payouts but cannot determine if a bet is wise. Successful betting requires research, discipline, and reasonable judgement about true probabilities versus the bookmaker's implied odds. For related financial calculations, explore our ROI calculator to track betting performance.
Gambling should be for entertainment with money you can afford to lose. If betting becomes problematic, resources like the National Council on Problem Gambling offer confidential support. Always bet responsibly within your means.
Last Updated: January 2026 | Reviewed for accuracy
Includes stake