You visit an American sportsbook and see "-150." You switch to a British bookmaker and it's "3/1." Back on a European site, and it's "2.50." Three ways of expressing the exact same thing — no wonder it gets confusing.
Here's the good news: all three formats represent exactly the same information. Once you understand the logic behind each one, converting between them becomes second nature.
In this guide, you'll learn how to switch between formats in seconds. You'll never be stumped by an odds format again.
The Three Formats at a Glance
| Format | Used Where | Example | What It Means |
|---|---|---|---|
| Decimal | Europe, Canada, Australia | 2.50 | Multiply your stake by 2.50 |
| American | United States | +150 or -200 | Profit per $100 or stake to win $100 |
| Fractional | United Kingdom, Ireland | 3/2 | Win $3 for every $2 wagered |
Each format has its own logic. Let's break them down.
1. Decimal Odds (Europe)
How They Work
This is the simplest format. The odds represent the multiplier applied to your stake, with your original wager included in the return.
Formula:
Total Return = Stake x Decimal Odds
Examples: - Odds 2.00 -> Bet $10, get back $20 (profit of $10) - Odds 1.50 -> Bet $10, get back $15 (profit of $5) - Odds 3.00 -> Bet $10, get back $30 (profit of $20)
Calculating Net Profit
If you only want the profit (without your stake):
Profit = Stake x (Odds - 1)
Example: Odds 2.50, stake $10 - Profit = $10 x (2.50 - 1) = $10 x 1.50 = $15 profit
Calculating Implied Probability
As explained in our guide on how odds are calculated, every odds price represents a probability:
Probability = 1 / Decimal Odds x 100
| Decimal Odds | Implied Probability |
|---|---|
| 1.50 | 66.7% |
| 2.00 | 50% |
| 2.50 | 40% |
| 3.00 | 33.3% |
| 4.00 | 25% |
| 5.00 | 20% |
2. American Odds (USA)
How They Work
This is the most confusing format at first, but it makes perfect sense once you get it. There are two types:
Positive odds (+150, +200, etc.) - Show the profit on a $100 bet - +150 means: bet $100, win $150 profit (total return $250)
Negative odds (-150, -200, etc.) - Show the stake required to win $100 - -150 means: bet $150 to win $100 profit (total return $250)
The Logic Behind the System
- Positive odds = underdog (less than 50% chance)
- Negative odds = favorite (more than 50% chance)
The higher the number (in absolute value), the further from a coin flip: - +300 -> big underdog - -300 -> heavy favorite - +100 / -100 -> even money (equivalent to 2.00 decimal)
Concrete Examples
| US Odds | Meaning | Decimal Equivalent |
|---|---|---|
| +100 | Bet $100, win $100 | 2.00 |
| +150 | Bet $100, win $150 | 2.50 |
| +200 | Bet $100, win $200 | 3.00 |
| -100 | Bet $100 to win $100 | 2.00 |
| -150 | Bet $150 to win $100 | 1.67 |
| -200 | Bet $200 to win $100 | 1.50 |
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3. Fractional Odds (UK)
How They Work
Fractional odds show the profit-to-stake ratio. The first number is the potential profit, the second is the stake.
Format: Profit / Stake
Examples: - 3/1 (read "three to one") -> Win $3 for every $1 wagered - 1/2 -> Win $1 for every $2 wagered (i.e., $0.50 per dollar) - 5/2 -> Win $5 for every $2 wagered (i.e., $2.50 per dollar)
Calculating the Total Return
Total Return = Stake + (Stake x Numerator / Denominator)
Example: Odds 5/2, stake $10 - Profit = $10 x (5 / 2) = $10 x 2.5 = $25 - Total return = $10 + $25 = $35
Special Cases
- Evens (or 1/1): You double your money — equivalent to 2.00 decimal
- Odds-on (e.g., 1/3): The profit is less than the stake — this is a heavy favorite
The Conversion Formulas
Decimal -> American
If decimal odds >= 2.00:
US Odds = (Decimal - 1) x 100
Example: 2.50 -> (2.50 - 1) x 100 = +150
If decimal odds < 2.00:
US Odds = -100 / (Decimal - 1)
Example: 1.50 -> -100 / (1.50 - 1) = -100 / 0.50 = -200
American -> Decimal
If positive (+):
Decimal = (US / 100) + 1
Example: +150 -> (150 / 100) + 1 = 1.5 + 1 = 2.50
If negative (-):
Decimal = (100 / |US|) + 1
Example: -200 -> (100 / 200) + 1 = 0.5 + 1 = 1.50
Decimal -> Fractional
Fractional = (Decimal - 1) expressed as a fraction
Example: 2.50 -> 2.50 - 1 = 1.5 = 3/2
Fractional -> Decimal
Decimal = (Numerator / Denominator) + 1
Example: 5/2 -> (5 / 2) + 1 = 2.5 + 1 = 3.50
Quick Conversion Table
Keep this table handy:
| Decimal | American | Fractional | Probability |
|---|---|---|---|
| 1.25 | -400 | 1/4 | 80% |
| 1.33 | -300 | 1/3 | 75% |
| 1.50 | -200 | 1/2 | 66.7% |
| 1.67 | -150 | 2/3 | 60% |
| 1.80 | -125 | 4/5 | 55.6% |
| 1.91 | -110 | 10/11 | 52.4% |
| 2.00 | +100 | 1/1 (Evens) | 50% |
| 2.10 | +110 | 11/10 | 47.6% |
| 2.20 | +120 | 6/5 | 45.5% |
| 2.50 | +150 | 3/2 | 40% |
| 3.00 | +200 | 2/1 | 33.3% |
| 4.00 | +300 | 3/1 | 25% |
| 5.00 | +400 | 4/1 | 20% |
| 10.00 | +900 | 9/1 | 10% |
Why This Matters for Bettors
1. Comparing Sportsbooks
The same game can be displayed differently depending on the site: - European site: 2.15 - American site: +115 - British site: 23/20
Without being able to convert, comparing is impossible. Yet finding the best price through line shopping can add several percentage points of ROI over the long run.
2. Understanding American Analysis
The vast majority of sports betting content and analysis comes from the United States. If you read a breakdown that mentions "-110 juice" or "+EV at +180," you need to understand what that means instantly.
3. Calculating Your Payouts Quickly
Some sites don't have a built-in payout calculator. Being able to convert odds mentally saves time and prevents costly errors.
The 2.00 Anchor Point Trick
Remember this: 2.00 decimal = +100 American = 1/1 fractional = 50%
This is your anchor point. From there:
- Odds above 2.00 -> underdog -> positive US odds
- Odds below 2.00 -> favorite -> negative US odds
If you see +150, you immediately know it's "above 2.00," so somewhere between 2.00 and 3.00. More precisely, 2.50.
How ProbWin Displays Odds
At ProbWin, we display odds in decimal format by default — it's the most readable and the easiest to convert into a probability.
When we identify a value bet, we show: - The bookmaker's odds (decimal) - The implied probability of that price - Our model's estimated probability - The edge in percentage points
This transparency lets you understand exactly why a bet represents value.
Common Mistakes to Avoid
Confusing Profit with Total Return
- Decimal 2.50 -> Total return = 2.50x the stake (profit = 1.50x)
- US +150 -> Profit = 1.50x the stake (total return = 2.50x)
- Fractional 3/2 -> Profit = 1.5x the stake (total return = 2.5x)
All three say the same thing, but decimal includes the stake; the others don't.
Forgetting the Sign on American Odds
+150 and -150 are very different: - +150 = 2.50 decimal (underdog) - -150 = 1.67 decimal (favorite)
Not Checking the Site's Format
Some sites let you switch the display format in your settings. Before placing a bet, always verify which format you're looking at.
Conclusion
You now have a solid grasp of all three odds formats:
- Decimal: The simplest — a multiplier on your stake
- American: Based on $100 — positive for underdogs, negative for favorites
- Fractional: Profit-to-stake ratio — the traditional UK format
Converting becomes natural with practice. In the meantime, keep the reference table within reach.
What really matters isn't the format — it's what the odds represent. As we covered in our guide on how odds are calculated, every price is a probability in disguise. And your job as a sharp bettor is to find the odds that underestimate the true probability — that's the core principle of value betting.
Ready for the next step? Learn how bookmakers make money through the margin built into every price.
