Odds Converter

Convert between American, decimal, fractional, implied probability, and prediction market cents instantly. Supports two-sided vig analysis.

Enter odds in any format to see conversions. Try: +150, 2.50, 3/2, 40%, or 40¢

How to Use the Odds Converter

Enter odds in any format and this tool converts them to all five standard representations. The converter auto-detects your input format based on the syntax: use a +/- prefix for American, a decimal point for decimal, a slash for fractional, a % sign for implied probability, or a ¢ suffix for prediction market cents.

Enable two-sided mode to enter both sides of a market. The tool calculates the overround (total implied probability), the vig percentage, and the no-vig fair odds for each side. This is useful for evaluating whether a sportsbook or prediction market is offering fair prices.

When Should You Use This Tool?

Use the odds converter when comparing lines across platforms that display odds in different formats. Sportsbooks typically show American odds, European books show decimal, and prediction markets show cent prices. This tool unifies them so you can compare apples to apples. The Odds Reference dashboard aggregates odds from multiple platforms in real time.

Frequently Asked Questions

What are American odds?
American odds use a plus/minus format relative to $100. A +150 line means a $100 bet wins $150 profit. A -200 line means you must bet $200 to win $100 profit. Positive numbers indicate underdogs; negative numbers indicate favorites.
How do decimal odds work?
Decimal odds represent the total payout per $1 wagered, including your stake. Odds of 2.50 mean a $1 bet returns $2.50 total ($1.50 profit + $1.00 stake). They are the standard format in Europe, Australia, and on prediction market platforms.
What are prediction market cents?
Prediction market platforms like Kalshi and Polymarket price contracts in cents from 1¢ to 99¢. A contract priced at 40¢ implies a 40% probability. If the event occurs, the contract pays out $1.00, yielding a 60¢ profit on a 40¢ investment.
How do I convert American odds to decimal?
For positive American odds, divide by 100 and add 1. So +150 becomes 1.50 + 1 = 2.50. For negative American odds, divide 100 by the absolute value and add 1. So -200 becomes 100/200 + 1 = 1.50.
What is implied probability?
Implied probability is the likelihood of an outcome as estimated by the odds. It equals 1 divided by the decimal odds. Decimal odds of 2.50 imply a 40% probability (1/2.50 = 0.40). Sportsbook implied probabilities sum to more than 100% due to the vig.
What is the vig (juice)?
The vig, also called juice or overround, is the margin built into odds by the bookmaker. In a fair coin-flip market, both sides would be +100 (2.00 decimal). A sportsbook might offer -110 on each side, creating a ~4.5% vig that guarantees their profit regardless of outcome.
How do fractional odds work?
Fractional odds, common in UK betting, express profit relative to stake. Odds of 3/2 mean you win $3 for every $2 wagered (plus your $2 back). This is equivalent to +150 American or 2.50 decimal.
Why do prediction market prices not always add to 100%?
On platforms like Polymarket, YES and NO prices for a binary market should theoretically sum to $1.00 (100%). In practice, they may differ slightly due to the bid-ask spread in the orderbook. This spread functions similarly to the vig in traditional sportsbooks.

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