Betting Odds Calculator
Convert betting odds between American, Decimal, and Fractional formats. Calculate implied probability, potential payouts, break-even win rate, and identify value bets with our free odds converter.
Enter odds above to convert between formats and calculate implied probability
Examples: +150, -110, 2.50, 1.91, 3/2, 10/11
Quick Odds Reference
| American | Decimal | Fractional | Probability | $100 Profit |
|---|---|---|---|---|
| -300 | 1.33 | 1/3 | 75.0% | $33.33 |
| -200 | 1.50 | 1/2 | 66.7% | $50.00 |
| -150 | 1.67 | 2/3 | 60.0% | $66.67 |
| -110 | 1.91 | 10/11 | 52.4% | $90.91 |
| +100 | 2.00 | 1/1 | 50.0% | $100.00 |
| +150 | 2.50 | 3/2 | 40.0% | $150.00 |
| +200 | 3.00 | 2/1 | 33.3% | $200.00 |
| +300 | 4.00 | 3/1 | 25.0% | $300.00 |
| +500 | 6.00 | 5/1 | 16.7% | $500.00 |
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About This Calculator
Understanding betting odds is the foundation of successful sports betting, yet millions of bettors place wagers without truly comprehending what the numbers mean. Whether you're seeing -110, 2.50, or 3/2, these formats all represent the same thing: the implied probability of an outcome and your potential return. Americans alone wagered over $119 billion legally on sports in 2023, with the average bettor giving up 4-10% of their bankroll to the bookmaker's margin without even realizing it.
Our Betting Odds Calculator instantly converts between American (moneyline), Decimal, and Fractional odds formats while revealing the hidden mathematics bookmakers use to ensure their profit. Enter any odds format and immediately see the implied probability, potential payout on any stake, break-even win rate, and whether the odds represent value. More importantly, use our vig calculator to expose exactly how much the sportsbook is taking from each market - knowledge that separates recreational bettors from those who actually profit long-term.
How to Use the Betting Odds Calculator
- 1Enter your odds in any format (American like +150/-150, Decimal like 2.50, or Fractional like 3/2).
- 2The calculator auto-detects the format, or manually select the format if needed.
- 3View instant conversions to all three odds formats.
- 4Check the implied probability to understand the true likelihood the bookmaker has assigned.
- 5See potential payouts for any stake amount (default $100).
- 6Review the break-even win rate you need to profit at these odds.
- 7Use the two-way odds comparison to calculate the vig/overround in any market.
- 8Identify value by comparing implied probability to your estimated probability.
Formula
Implied Probability = Risk / (Risk + Potential Win) x 100This fundamental formula reveals what odds truly represent: the probability a bookmaker has assigned to an outcome. For negative American odds like -150, the implied probability is 150/(150+100) = 60%. For positive odds like +200, it's 100/(200+100) = 33.3%. When you add up the implied probabilities for all outcomes in a market, the total exceeds 100% - this excess is the bookmaker's margin (vig). A market with -110/-110 on both sides has total implied probability of 104.76%, meaning the book takes 4.76% regardless of outcome.
Understanding the Three Odds Formats
American Odds (Moneyline)
American odds are expressed as positive or negative numbers relative to $100:
Negative odds (-150, -200, -300):
- The number shows how much you must risk to win $100
- -150 means risk $150 to win $100 (total return $250)
- -200 means risk $200 to win $100 (total return $300)
- The larger the negative number, the bigger the favorite
Positive odds (+150, +200, +300):
- The number shows how much you win on a $100 bet
- +150 means risk $100 to win $150 (total return $250)
- +200 means risk $100 to win $200 (total return $300)
- The larger the positive number, the bigger the underdog
Even odds (+100 or -100):
- Risk $100 to win $100
- True 50/50 proposition (before vig)
Decimal Odds (European)
Decimal odds represent your total return per unit staked, including your original stake:
- 2.50 = For every $1 bet, you receive $2.50 back (including your $1 stake)
- Profit = (Decimal Odds - 1) x Stake
- Example: $100 at 2.50 = $250 total return, $150 profit
Key decimal benchmarks:
| Decimal | Equivalent American | Implied Probability |
|---|---|---|
| 1.50 | -200 | 66.7% |
| 2.00 | +100 (even) | 50.0% |
| 2.50 | +150 | 40.0% |
| 3.00 | +200 | 33.3% |
| 4.00 | +300 | 25.0% |
Decimal odds are preferred in Europe and on betting exchanges because they make calculating returns on parlays/accumulators simple: just multiply all the decimal odds together.
Fractional Odds (UK)
Fractional odds show your potential profit relative to your stake:
- 5/1 (five-to-one) = Win $5 for every $1 staked
- 3/2 (three-to-two) = Win $3 for every $2 staked
- 1/2 (one-to-two) = Win $1 for every $2 staked (odds-on favorite)
Reading fractional odds:
- The first number is potential profit
- The second number is the stake required
- Total return = Stake + (Stake x Fraction)
Common fractional conversions:
| Fractional | Decimal | American |
|---|---|---|
| 1/1 (evens) | 2.00 | +100 |
| 2/1 | 3.00 | +200 |
| 5/2 | 3.50 | +250 |
| 1/2 | 1.50 | -200 |
| 4/9 | 1.44 | -225 |
Odds Conversion Formulas
American to Decimal:
For positive American odds:
Decimal = (American / 100) + 1
Example: +150 = (150/100) + 1 = 2.50
For negative American odds:
Decimal = (100 / |American|) + 1
Example: -150 = (100/150) + 1 = 1.667
Decimal to American:
If decimal >= 2.00:
American = (Decimal - 1) x 100 (positive)
Example: 2.50 = (2.50 - 1) x 100 = +150
If decimal < 2.00:
American = -100 / (Decimal - 1) (negative)
Example: 1.50 = -100 / (1.50 - 1) = -200
Decimal to Fractional:
Fractional = (Decimal - 1) / 1
Then simplify to lowest terms.
Example: 2.50 = (2.50 - 1) / 1 = 3/2
Fractional to Decimal:
Decimal = (Numerator / Denominator) + 1
Example: 5/2 = (5/2) + 1 = 3.50
Quick Reference Table:
| American | Decimal | Fractional | Implied Prob |
|---|---|---|---|
| -500 | 1.20 | 1/5 | 83.3% |
| -400 | 1.25 | 1/4 | 80.0% |
| -300 | 1.33 | 1/3 | 75.0% |
| -200 | 1.50 | 1/2 | 66.7% |
| -150 | 1.67 | 2/3 | 60.0% |
| -110 | 1.91 | 10/11 | 52.4% |
| +100 | 2.00 | 1/1 | 50.0% |
| +110 | 2.10 | 11/10 | 47.6% |
| +150 | 2.50 | 3/2 | 40.0% |
| +200 | 3.00 | 2/1 | 33.3% |
| +300 | 4.00 | 3/1 | 25.0% |
| +500 | 6.00 | 5/1 | 16.7% |
| +1000 | 11.00 | 10/1 | 9.1% |
Implied Probability: The Key to Value Betting
What Is Implied Probability?
Implied probability is the likelihood of an outcome as suggested by the betting odds. It's the most important concept in sports betting because it allows you to compare what the bookmaker thinks will happen versus what you think will happen.
Calculating Implied Probability:
From American odds:
- Negative: Implied % = |Odds| / (|Odds| + 100) x 100
- Positive: Implied % = 100 / (Odds + 100) x 100
From Decimal odds:
- Implied % = (1 / Decimal) x 100
From Fractional odds:
- Implied % = Denominator / (Numerator + Denominator) x 100
Examples:
| Odds | Calculation | Implied Probability |
|---|---|---|
| -150 | 150/(150+100) | 60.0% |
| +200 | 100/(200+100) | 33.3% |
| 2.50 | 1/2.50 | 40.0% |
| 5/2 | 2/(5+2) | 28.6% |
Finding Value: The Golden Rule
Value exists when your estimated probability exceeds the implied probability:
Example scenario:
- Odds offered: +150 (implied probability 40%)
- Your analysis suggests: 50% chance of winning
- Expected value: +25% edge per bet
The Value Formula:
Expected Value = (Your Probability x Potential Win) - ((1 - Your Probability) x Stake)
If you bet $100 at +150 with a true 50% probability:
- EV = (0.50 x $150) - (0.50 x $100)
- EV = $75 - $50 = +$25 per bet
Over 100 such bets, you'd expect to profit $2,500.
Why Most Bettors Lose
The typical bettor:
- Sees a team they "feel good about"
- Bets without calculating implied probability
- Accepts whatever odds are offered
- Doesn't track their break-even requirements
The profitable bettor:
- Calculates implied probability for every bet
- Only bets when their probability exceeds implied probability
- Shops for the best odds across multiple sportsbooks
- Understands they need to beat the vig, not just pick winners
The Vig (Juice/Overround) Explained
What Is the Vig?
The vig (vigorish), also called juice, margin, or overround, is the bookmaker's built-in profit margin. It's why you can't simply flip a coin and profit betting on coin flips - the book ensures they win regardless of outcome.
How the Vig Works:
In a theoretically fair market:
- Team A: +100 (50% implied probability)
- Team B: +100 (50% implied probability)
- Total: 100% (no vig)
In a real sportsbook market:
- Team A: -110 (52.38% implied probability)
- Team B: -110 (52.38% implied probability)
- Total: 104.76% (4.76% vig)
Calculating the Vig:
Vig = Total Implied Probability - 100%
Vig = (1/Decimal1 + 1/Decimal2) x 100 - 100
Example with -110/-110:
- Decimal odds: 1.909 / 1.909
- Implied: (1/1.909) + (1/1.909) = 0.5238 + 0.5238 = 1.0476
- Vig = 104.76% - 100% = 4.76%
Typical Vig by Market Type:
| Market Type | Typical Vig | Your Break-Even |
|---|---|---|
| NFL point spread | 4-5% | 52-53% |
| NFL moneyline | 3-5% | 51-53% |
| NBA point spread | 4-5% | 52-53% |
| MLB moneyline | 4-6% | 52-54% |
| Player props | 8-15% | 55-60% |
| Futures/outrights | 15-40% | 60-80% |
| Live/in-play | 5-10% | 53-58% |
Calculating "True" Odds (Vig-Free)
To find what the odds would be without the vig:
- Calculate total implied probability (e.g., 104.76%)
- Divide each side's implied probability by the total
- Convert back to odds
Example:
- Team A: -150 (60.0% implied)
- Team B: +130 (43.5% implied)
- Total: 103.5%
True probabilities:
- Team A: 60.0% / 103.5% = 58.0%
- Team B: 43.5% / 103.5% = 42.0%
True (vig-free) odds:
- Team A: -138 (from 58.0%)
- Team B: +138 (from 42.0%)
Why the Vig Matters
At -110/-110:
- You need to win 52.38% to break even
- Winning 55% = +5% ROI
- Winning 50% = -4.5% ROI
Over 1,000 $100 bets at -110:
- 50% win rate: -$4,500 loss
- 52.4% win rate: Break even
- 55% win rate: +$5,000 profit
Every percentage point above break-even is pure profit; every point below is compounding losses.
Calculating Potential Payouts
Payout Calculation Formulas:
For American Odds:
Positive odds (+150):
Potential Win = Stake x (Odds / 100)
Total Return = Stake + Potential Win
Example: $100 at +150
- Potential win = $100 x (150/100) = $150
- Total return = $100 + $150 = $250
Negative odds (-150):
Potential Win = Stake x (100 / |Odds|)
Total Return = Stake + Potential Win
Example: $100 at -150
- Potential win = $100 x (100/150) = $66.67
- Total return = $100 + $66.67 = $166.67
For Decimal Odds:
Total Return = Stake x Decimal Odds
Potential Win = Total Return - Stake
Example: $100 at 2.50
- Total return = $100 x 2.50 = $250
- Potential win = $250 - $100 = $150
For Fractional Odds:
Potential Win = Stake x (Numerator / Denominator)
Total Return = Stake + Potential Win
Example: $100 at 5/2
- Potential win = $100 x (5/2) = $250
- Total return = $100 + $250 = $350
Payout Reference Table ($100 Stake):
| American | Decimal | Fractional | Win | Total Return |
|---|---|---|---|---|
| -300 | 1.33 | 1/3 | $33.33 | $133.33 |
| -200 | 1.50 | 1/2 | $50.00 | $150.00 |
| -150 | 1.67 | 2/3 | $66.67 | $166.67 |
| -110 | 1.91 | 10/11 | $90.91 | $190.91 |
| +100 | 2.00 | 1/1 | $100.00 | $200.00 |
| +150 | 2.50 | 3/2 | $150.00 | $250.00 |
| +200 | 3.00 | 2/1 | $200.00 | $300.00 |
| +300 | 4.00 | 3/1 | $300.00 | $400.00 |
| +500 | 6.00 | 5/1 | $500.00 | $600.00 |
| +1000 | 11.00 | 10/1 | $1,000.00 | $1,100.00 |
Break-Even Win Rate:
To profit long-term, you must win more often than the break-even rate:
Break-Even % = Risk / Total Return x 100
| Odds | Break-Even Win Rate |
|---|---|
| -200 | 66.7% |
| -150 | 60.0% |
| -110 | 52.4% |
| +100 | 50.0% |
| +110 | 47.6% |
| +150 | 40.0% |
| +200 | 33.3% |
| +300 | 25.0% |
Identifying Value Bets: A Practical Guide
What Makes a Bet "Value"?
A value bet occurs when the probability of an outcome is greater than what the odds imply. It's not about picking winners - it's about finding mispriced odds.
The Value Betting Framework:
- Calculate implied probability from the offered odds
- Estimate your own probability based on research/models
- Compare: If your probability > implied probability, you have value
- Calculate edge: Your Probability - Implied Probability = Edge
- Size appropriately: Larger edges warrant larger bets (Kelly Criterion)
Example Value Bet Analysis:
Scenario: NFL game, Team A vs Team B
- Sportsbook odds: Team A +150 (40% implied)
- Your analysis: Team A has 48% chance to win
Value calculation:
- Your edge: 48% - 40% = 8%
- Expected value per $100: $12
This is a clear value bet. Even if Team A loses this particular game, betting +8% edges consistently will profit over time.
Common Sources of Value:
- Line movement timing: Bet early when lines are soft, before sharps move them
- Injury/weather information: React faster than the market
- Public bias: Fade heavily bet public teams getting worse odds
- Statistical models: Find edges the market has missed
- Alternate lines: Sometimes -2.5 offers better value than -3.5
- Cross-sport knowledge: Specialists beat generalists
Red Flags (Likely Not Value):
- Betting favorites you "like" without calculating edge
- Following "expert picks" from tipsters
- Parlays (compounding vig destroys value)
- Teasers on "obvious" games
- Any bet where you can't articulate why it's value
Kelly Criterion: Optimal Bet Sizing
Once you identify value, the Kelly Criterion tells you how much to bet:
Kelly % = (Edge / Odds to 1) = (bp - q) / b
Where:
- b = decimal odds - 1
- p = your probability of winning
- q = probability of losing (1 - p)
Example:
- Odds: +150 (b = 1.5)
- Your probability: 48% (p = 0.48)
- q = 0.52
Kelly = (1.5 x 0.48 - 0.52) / 1.5 = 0.20 / 1.5 = 13.3% of bankroll
Most professionals use "fractional Kelly" (25-50% of full Kelly) to reduce variance.
Line Shopping: The Easiest Edge in Sports Betting
What Is Line Shopping?
Line shopping means comparing odds across multiple sportsbooks before placing a bet. It's the single easiest way to improve your betting results without any additional handicapping skill.
Why Lines Differ Between Books:
- Different models: Books calculate odds differently
- Risk management: Books adjust to balance their liability
- Sharp action: Some books get bet earlier by professionals
- Market positioning: Some books offer better odds to attract customers
Real-World Example:
You want to bet on the Chiefs moneyline:
- DraftKings: -145
- FanDuel: -150
- BetMGM: -148
- Caesars: -140
Impact of taking -140 vs -150:
- At -150: Break-even requires 60.0% win rate
- At -140: Break-even requires 58.3% win rate
- Difference: 1.7% edge gained instantly
Over 500 bets, that 1.7% difference at $100/bet = $850 in extra profit
Line Shopping Best Practices:
-
Have accounts at 4-6 sportsbooks minimum
- Major books: DraftKings, FanDuel, BetMGM, Caesars
- Sharper books: Circa, Pinnacle (where legal), Bookmaker
-
Use odds comparison tools
- Compare lines in real-time before betting
- Set alerts for line movements
-
Time your bets strategically
- NFL: Bet Sundays early morning for best selection
- NBA: Bet early afternoon for opener value
- MLB: Bet early for starting pitcher confirmation
-
Track your line shopping results
- Note what odds you got vs. market average
- Calculate your "odds edge" over time
Expected Value of Line Shopping:
Professional bettors estimate line shopping adds 1-3% to ROI. On $50,000 annual volume:
- 1% improvement = $500 extra profit
- 2% improvement = $1,000 extra profit
- 3% improvement = $1,500 extra profit
For zero additional handicapping effort.
Half-Point Values in Point Spread Betting:
Key numbers in NFL (touchdown/field goal increments):
- Getting +3.5 vs +3: Worth 6% in win probability
- Getting +7.5 vs +7: Worth 4% in win probability
- Getting -2.5 vs -3: Worth 5% in win probability
Never accept a bad number on a key number game - shop for it or pass.
Pro Tips
- 💡Always calculate implied probability before betting - if you can't articulate the implied probability, you shouldn't place the bet.
- 💡At -110 odds, you need to win 52.4% of your bets to break even - not 50%. Every bet must overcome this hurdle.
- 💡Line shop across multiple sportsbooks. Getting -105 instead of -110 adds roughly 2.5% to your ROI over time.
- 💡The vig on player props and futures is often 2-3x higher than point spreads - be extra selective with these markets.
- 💡Track your closing line value (CLV), not just your win rate. Consistently beating closing lines predicts long-term profit better than short-term results.
- 💡Avoid parlays for serious betting - they compound the vig and dramatically reduce your expected value.
- 💡Focus on finding value (+EV), not just picking winners. A profitable bet can lose; an unprofitable bet can win.
- 💡Key numbers in NFL point spreads (3, 7, 10) are worth extra attention - never accept a bad number on these.
- 💡Bet early for the best selection of lines and to capture value before sharp money moves the market.
- 💡Use fractional Kelly Criterion (25-50% of full Kelly) to size bets - this balances growth with bankroll protection.
Frequently Asked Questions
American odds use positive and negative numbers based on a $100 reference. Negative odds (like -150) tell you how much you must risk to win $100 - so at -150, you risk $150 to win $100. Positive odds (like +150) tell you how much you win on a $100 bet - so at +150, you win $150 on a $100 wager. The key insight is that negative odds indicate favorites (higher probability of winning, lower payout), while positive odds indicate underdogs (lower probability, higher payout). At -110, the standard for point spreads, you risk $110 to win $100, which builds in the bookmaker's profit margin.
