What Is a Betting Odds Calculator?
A betting odds calculator helps you:
- Calculate potential payouts from any stake and odds
- Convert odds between decimal, fractional, and American formats
- Find implied probability - what the odds suggest about winning chances
- Calculate bookmaker margin - the edge built into odds
This is an essential tool for understanding any bet before you place it.
Understanding Odds Formats
Decimal Odds (European)
Most common worldwide. Shows total return for every $1 wagered.
| Decimal Odds | $100 Bet Return | Profit |
|---|---|---|
| 1.50 | $150 | $50 |
| 2.00 | $200 | $100 |
| 3.00 | $300 | $200 |
| 5.00 | $500 | $400 |
Formula: Return = Stake × Decimal Odds
Implied Probability: 1 / Decimal Odds × 100
Fractional Odds (UK)
Traditional UK format. Shows profit relative to stake.
| Fractional | Meaning | Decimal Equivalent |
|---|---|---|
| 1/1 (Evens) | Win $1 for every $1 staked | 2.00 |
| 2/1 | Win $2 for every $1 staked | 3.00 |
| 1/2 | Win $1 for every $2 staked | 1.50 |
| 5/2 | Win $5 for every $2 staked | 3.50 |
| 9/4 | Win $9 for every $4 staked | 3.25 |
Formula: Profit = Stake × (Numerator / Denominator)
American Odds (Moneyline)
US format. Positive shows profit on $100 bet; negative shows stake needed to win $100.
| American | Meaning | Decimal |
|---|---|---|
| +150 | $100 bet wins $150 profit | 2.50 |
| +200 | $100 bet wins $200 profit | 3.00 |
| -150 | Bet $150 to win $100 profit | 1.67 |
| -200 | Bet $200 to win $100 profit | 1.50 |
| +100 | $100 bet wins $100 profit (Evens) | 2.00 |
Formulas:
- Positive: Decimal = (American / 100) + 1
- Negative: Decimal = (100 / |American|) + 1
Odds Conversion Table
| Decimal | Fractional | American | Implied Probability |
|---|---|---|---|
| 1.25 | 1/4 | -400 | 80.0% |
| 1.33 | 1/3 | -300 | 75.0% |
| 1.50 | 1/2 | -200 | 66.7% |
| 1.67 | 2/3 | -150 | 60.0% |
| 1.80 | 4/5 | -125 | 55.6% |
| 1.91 | 10/11 | -110 | 52.4% |
| 2.00 | 1/1 | +100 | 50.0% |
| 2.10 | 11/10 | +110 | 47.6% |
| 2.50 | 3/2 | +150 | 40.0% |
| 3.00 | 2/1 | +200 | 33.3% |
| 4.00 | 3/1 | +300 | 25.0% |
| 5.00 | 4/1 | +400 | 20.0% |
| 6.00 | 5/1 | +500 | 16.7% |
| 10.00 | 9/1 | +900 | 10.0% |
| 21.00 | 20/1 | +2000 | 4.8% |
Calculating Potential Payouts
Decimal Odds Payout
Total Return = Stake × Decimal Odds
Profit = Total Return - Stake
Example: $50 at 2.40 odds
- Return: $50 × 2.40 = $120
- Profit: $120 - $50 = $70
Fractional Odds Payout
Profit = Stake × (Numerator / Denominator)
Total Return = Profit + Stake
Example: $50 at 7/4 odds
- Profit: $50 × (7/4) = $87.50
- Return: $87.50 + $50 = $137.50
American Odds Payout
Positive odds (+):
Profit = Stake × (American / 100)
Example: $50 at +180
- Profit: $50 × (180/100) = $90
- Return: $90 + $50 = $140
Negative odds (-):
Profit = Stake × (100 / |American|)
Example: $50 at -150
- Profit: $50 × (100/150) = $33.33
- Return: $33.33 + $50 = $83.33
Implied Probability
Implied probability shows what the odds suggest about an outcome’s chances.
Calculating Implied Probability
| Format | Formula |
|---|---|
| Decimal | 1 / Odds × 100 |
| Fractional | Denominator / (Numerator + Denominator) × 100 |
| American (+) | 100 / (American + 100) × 100 |
| American (-) | |American| / (|American| + 100) × 100 |
Examples
Decimal 2.50:
1 / 2.50 × 100 = 40%
Fractional 3/1:
1 / (3 + 1) × 100 = 25%
American +200:
100 / (200 + 100) × 100 = 33.3%
American -150:
150 / (150 + 100) × 100 = 60%
Bookmaker Margin (Overround)
Bookmakers build a profit margin into odds. This is called the “overround” or “vig.”
How to Calculate Margin
Add the implied probabilities of all outcomes:
Margin = (1/Odds1 + 1/Odds2 + ...) × 100 - 100%
Example: Football Match
| Outcome | Decimal Odds | Implied Probability |
|---|---|---|
| Home Win | 2.10 | 47.6% |
| Draw | 3.40 | 29.4% |
| Away Win | 3.50 | 28.6% |
| Total | 105.6% |
Margin: 105.6% - 100% = 5.6%
This means for every $100 wagered across all outcomes, the bookmaker expects to keep $5.60.
Typical Bookmaker Margins
| Market Type | Typical Margin |
|---|---|
| Major football | 2-5% |
| Tennis | 3-6% |
| Horse racing | 10-20% |
| Niche sports | 5-10% |
| Live betting | 5-10% |
Lower margin = better value for bettors
Finding Value Bets
A value bet exists when your estimated probability is higher than the implied probability.
Value Calculation
Value = (Your Probability × Decimal Odds) - 1
If Value > 0: Bet has positive expected value
Example
- Odds: 3.00 (implied probability: 33.3%)
- Your estimate: 40% chance of winning
Value = (0.40 × 3.00) - 1 = 1.20 - 1 = +0.20 (20% value)
This is a value bet - you estimate 40% chance but only need 33.3% to break even.
Parlay Odds Calculator
For multiple selections (accumulators):
Combined Decimal Odds = Odds1 × Odds2 × Odds3 × ...
Example: 3-Leg Parlay
| Selection | Decimal Odds |
|---|---|
| Bet 1 | 1.80 |
| Bet 2 | 2.10 |
| Bet 3 | 1.65 |
Combined odds: 1.80 × 2.10 × 1.65 = 6.24
$10 bet returns: $10 × 6.24 = $62.40
Calculating Stake from Desired Profit
Want to win a specific amount? Calculate the required stake:
Stake = Desired Profit / (Decimal Odds - 1)
Example
Want to win $100 at 2.50 odds:
Stake = $100 / (2.50 - 1) = $100 / 1.50 = $66.67
Quick Reference Tables
Stake to Win $100
| Decimal Odds | Stake Needed |
|---|---|
| 1.50 | $200.00 |
| 1.80 | $125.00 |
| 2.00 | $100.00 |
| 2.50 | $66.67 |
| 3.00 | $50.00 |
| 4.00 | $33.33 |
| 5.00 | $25.00 |
Return on $100 Stake
| Decimal Odds | Total Return | Profit |
|---|---|---|
| 1.50 | $150 | $50 |
| 2.00 | $200 | $100 |
| 2.50 | $250 | $150 |
| 3.00 | $300 | $200 |
| 5.00 | $500 | $400 |
| 10.00 | $1,000 | $900 |
Frequently Asked Questions
What are the best odds format?
Decimal odds are easiest to calculate with. Multiply stake by odds to get total return. Most online betting sites let you choose your preferred format.
How do I know if odds are good?
Compare implied probability to your own assessment. If you think a team has 50% chance but odds imply 40%, that’s good value. Also compare odds across bookmakers.
Why do different bookmakers have different odds?
Bookmakers have different opinions, different customer bases, and different margins. Shopping for the best odds across multiple books increases your long-term returns.
What does -110 mean?
American odds of -110 mean you bet $110 to win $100 profit. This is the standard vig on point spreads. It equals 1.91 decimal or 10/11 fractional.
How do bookmakers make money?
Through the margin (overround) built into odds. The implied probabilities of all outcomes add up to more than 100%, guaranteeing the bookmaker profit over time.
Should I always take the highest odds?
Generally yes, but consider other factors like bookmaker reliability, betting limits, and bonus offers. A slightly lower odds with a trusted bookmaker may be preferable.
Start Calculating Your Bets
Use our free betting odds calculator above to:
- Enter odds in any format (decimal, fractional, American)
- See instant conversions between all formats
- Calculate potential payouts for any stake
- Find the implied probability
- Understand what odds mean before betting
The calculator makes it easy to compare value across different bookmakers and make informed betting decisions.