Odds Calculator

Quick Answer

Last updated: 10 November 2026 ·How we calculate this: standard conversions between American, decimal and fractional odds

How This Odds Calculator Works

Choose the format your odds are in, enter them and your stake. The calculator converts the odds to decimal, which is the simplest form, then shows them as American (moneyline) and fractional odds too. It gives the implied probability, the total payout including your stake, and the profit if the bet wins. Enter the odds on the other side of a two-way market to see the bookmaker’s margin and the fair, no-vig probability.

How to Use the Odds Calculator

1. Choose American, decimal or fractional odds.
2. Enter the odds and your stake.
3. Optionally, enter the odds on the other side of the market.
4. Press Calculate.
5. Read the implied probability, payout and the odds in every format.

Odds Conversion Formulas

• American + to decimal: 1 + odds ÷ 100
• American − to decimal: 1 + 100 ÷ |odds|
• Fractional A/B to decimal: 1 + A ÷ B
• Implied probability: 1 ÷ decimal odds (odds of A:B in favor give A ÷ (A + B))
• Payout: stake × decimal odds; profit: stake × (decimal odds − 1)

Key Terms

• Moneyline: American odds on which side wins, written with + or −.
• Implied probability: the chance of winning suggested by the odds, 1 ÷ decimal odds.
• Overround or vig: the bookmaker’s margin, the amount by which implied probabilities exceed 100%.
• Stake: the amount you bet.
• Payout: what you get back if you win, stake included.

Worked Example

A team is +150 and its opponent is −180. You bet $100 on the team at +150.

• Decimal odds = 1 + 150 ÷ 100 = 2.50; implied probability = 1 ÷ 2.50 = 40%
• Payout = $100 × 2.50 = $250, so the profit is $150
• The other side: 1 + 100 ÷ 180 = 1.5556, implied 64.29%
• Together they add to 104.29%, so the bookmaker’s margin is about 4.29%, and the fair chance for the team is 38.36%.

Real-Life Examples

• Underdog: +250 is decimal 3.5, an implied 28.57% chance; $20 returns $70.00.
• Favorite: −150 is decimal 1.6667, an implied 60.00%; $60 wins $40.00.
• Horse racing: 7/2 is decimal 4.5, about 22.2% implied.
• Even money: +100, 2.00 and 1/1 all mean a 50% implied chance.

American vs Decimal vs Fractional Odds

• American (moneyline): used in the US; + shows profit on $100, − shows the stake needed to win $100.
• Decimal: common in Europe, Canada and Australia; shows the total return per $1, stake included.
• Fractional: traditional in the UK and Ireland, especially for horse racing; shows profit per unit staked.

Odds Conversion Chart

Why Implied Probabilities Add Up to More Than 100%

If odds were perfectly fair, the implied probabilities of every outcome would add up to exactly 100%. Bookmakers shade the odds so the total is higher, often a few percent for popular two-way markets. That extra, called the overround or vig, is how they earn money whatever the result. Removing it, by dividing each implied probability by the total, gives the market’s fair estimate of each outcome.

Remember that odds are prices, not predictions. Over time the margin means most bettors lose money, so treat betting as entertainment with money you can afford to lose. Help is available from the National Problem Gambling Helpline at 1-800-GAMBLER in the US.

Common Mistakes to Avoid

• Treating implied probability as the true chance. It includes the bookmaker’s margin.
• Confusing payout and profit. Payout includes your stake.
• Reading −200 as a profit. Minus odds show the stake needed to win $100.
• Entering American odds between −100 and +100. They do not exist.
• Chasing losses. Set a budget and stick to it.

Frequently Asked Questions

References & Sources