Universal Odds Converter
Convert between American, Decimal, and Fractional odds formats instantly
Enter Odds in Any Format
Quick Examples
What are Betting Odds?
Betting odds represent the probability of an outcome and determine how much you can win from a bet. Bookmakers set odds based on statistical analysis, but different regions use different formats to express the same probability. Understanding how to convert between formats helps you compare odds across different sportsbooks and markets.
Odds Conversion Formulas
Decimal to American:
- If decimal ≥ 2.00: American = (decimal - 1) × 100
- If decimal < 2.00: American = -100 / (decimal - 1)
Fractional to Decimal:
- Decimal = (numerator / denominator) + 1
Implied Probability:
- Probability (%) = (1 / decimal odds) × 100
Example: Decimal odds of 2.50 = 40% implied probability, +150 American, or 3/2 fractional
Understanding Odds Formats
American Odds
Used In: United States, Canada
Format: +/- relative to $100 stake
How to Read:
- Positive (+150): Win $150 on $100 bet
- Negative (-200): Bet $200 to win $100
- Even (+100/-100): Double your money
Favorites show negative odds, underdogs show positive odds
Decimal Odds
Used In: Europe, Australia, Canada
Format: Decimal number (1.50, 2.50, 3.00)
How to Read:
- Total Return: Stake × Decimal Odds
- Profit: (Decimal - 1) × Stake
- 2.00 odds: Even money (double stake)
Easiest format for calculating potential returns - includes original stake
Fractional Odds
Used In: United Kingdom, Ireland
Format: Fraction (5/2, 3/1, 10/11)
How to Read:
- 5/2: Win $5 for every $2 wagered
- 1/1 (Evens): Win equals stake
- 10/11: Win $10 for every $11 bet
Traditional format for horse racing - shows profit only, not total return
Real-World Conversion Examples
Example 1: Converting Favorite Odds
American: -200 (favorite to win)
Calculation: 1 + (100 / 200) = 1.50
Decimal: 1.50
Fractional: 1/2 (win $1 for every $2)
Probability: 66.67% chance to win
Example 2: Converting Underdog Odds
Fractional: 5/2 (strong underdog)
Calculation: (5 ÷ 2) + 1 = 3.50
Decimal: 3.50
American: +250
Probability: 28.57% chance to win
Example 3: Converting Even Money
Decimal: 2.00 (even odds)
Fractional: 1/1 (Evens)
American: +100 or -100
Probability: 50% chance to win
Return: $100 bet returns $200 total
Professional Tips for Using Odds
Compare Across Books
Different sportsbooks offer different odds for the same event. Always shop around and convert odds to find the best value, even if lines differ by just a few points.
Understand Implied Probability
Convert odds to implied probability to see the bookmaker's assessment. If your calculated probability is higher, you may have found value in the bet.
Watch for Vig (Juice)
The sum of implied probabilities for all outcomes exceeds 100% - the difference is the bookmaker's margin. Lower vig means better odds for bettors.
Use Decimal for Parlays
Decimal odds are easiest for calculating parlay payouts - just multiply all decimal odds together and multiply by your stake for total return.
Learn All Three Formats
Being fluent in all odds formats lets you quickly spot value across global betting markets and understand odds movements more intuitively.
Check Before Line Moves
Odds change based on betting volume and new information. Convert and compare odds early to lock in the best value before sharp money moves the line.
Common Odds Conversion Table
| American | Decimal | Fractional | Implied Probability |
|---|---|---|---|
| -500 | 1.20 | 1/5 | 83.33% |
| -300 | 1.33 | 1/3 | 75.00% |
| -200 | 1.50 | 1/2 | 66.67% |
| -150 | 1.67 | 4/6 | 60.00% |
| -110 | 1.91 | 10/11 | 52.38% |
| +100 | 2.00 | 1/1 | 50.00% |
| +150 | 2.50 | 3/2 | 40.00% |
| +200 | 3.00 | 2/1 | 33.33% |
| +300 | 4.00 | 3/1 | 25.00% |
| +500 | 6.00 | 5/1 | 16.67% |
Frequently Asked Questions
What are the different betting odds formats?
The three main betting odds formats are American (used in US, shown as +/- numbers), Decimal (used in Europe/Australia, shown as decimals like 2.50), and Fractional (used in UK, shown as fractions like 5/2). All three formats represent the same probability but are calculated and displayed differently.
How do I convert American odds to decimal odds?
For positive American odds, divide by 100 and add 1 (e.g., +150 becomes 2.50). For negative American odds, divide 100 by the absolute value and add 1 (e.g., -200 becomes 1.50). Our calculator does this conversion instantly for you.
What is implied probability in betting odds?
Implied probability is the likelihood of an outcome expressed as a percentage, as suggested by the betting odds. It's calculated from the odds and represents the bookmaker's assessment of how likely an event is to occur, including their built-in margin.
How do fractional odds work?
Fractional odds show profit relative to stake. For example, 5/2 odds mean you win $5 for every $2 wagered, plus your original stake back. To calculate total return, divide the first number by the second, multiply by your stake, then add your stake.
Which odds format is best for betting?
Decimal odds are generally easiest for calculating potential returns (just multiply stake by odds). American odds are standard in US sportsbooks. Fractional odds are traditional in horse racing. Use whichever format you're most comfortable with - they all represent the same probability.
How do bookmakers calculate odds?
Bookmakers use statistical models, historical data, and expert analysis to estimate the true probability of outcomes, then adjust the odds to include their profit margin (called the vig or overround). This is why the implied probabilities of all outcomes typically add up to more than 100%.