If you've ever stared at '+200' or '7/2' on a sportsbook screen and felt your brain short-circuit, you're not alone. Betting odds come in three different formats depending on where you live, but they all tell you the same two things: your potential payout and the implied probability of an outcome.
The Three Odds Formats at a Glance
| Format | Example | What It Means | Where It Is Used |
|---|---|---|---|
| American (positive) | +200 | Win $200 profit on a $100 bet | US, Canada |
| American (negative) | -150 | Bet $150 to win $100 profit | US, Canada |
| Decimal | 3.00 | Multiply your stake by 3.00 for total return | Europe, Australia, Canada |
| Fractional | 2/1 | Win $2 for every $1 staked | UK, Ireland |
How to Convert Between Formats
The math is straightforward once you know the rules. For American odds, positive numbers convert to decimal with `(odds / 100) + 1` — so **+200 becomes 3. 00**.
Negative odds use `(100 / |odds|) + 1` — so **-150 becomes 1. 667**. Fractional odds are just the decimal minus 1 expressed as a fraction: 3.
00 minus 1 is 2/1. An odds converter handles all three instantly, but learning the relationship helps you spot mispriced lines faster when shopping across sportsbooks.
What Is Implied Probability?
Implied probability is the percentage chance the odds represent. The formula is dead simple: `1 / decimal odds x 100`. Odds of **3.
00 imply a 33. 3% chance**. Odds of **1.
50 imply a 66. 7% chance**. This is the single most useful number for a bettor because it lets you ask the key question: 'Do I think the actual probability is higher or lower than what the odds say?
' If you believe an outcome has a 40% chance but the odds only imply 33. 3%, you've found a value bet.
Remember: implied probabilities from a bookmaker always add up to more than 100%. That extra percentage is the vig (vigorish), also called the overround. In a fair market, two equally likely outcomes would each be at +100 (50% implied probability each). In reality, you'll see both sides at -110, which works out to 52.4% each for a total of 104.8%. That 4.8% is the bookmaker's built-in profit.
Understanding the Vig and Why It Matters
Convert Odds Instantly
Use TheCalcUniverse Betting Odds Converter to switch between American, Decimal, and Fractional formats, see implied probability, and calculate your payout for any stake.