Convert MMA and boxing fight odds between American, decimal, and fractional formats. Calculate implied probability, vig-free odds, and potential payout from any odds format.
Understanding fight odds is essential for anyone following MMA, boxing, or any combat sport. Odds represent the probability of each fighter winning and determine the payout for a successful bet. Our MMA Fight Odds Converter Calculator converts between American (moneyline), decimal, and fractional odds formats—and reveals the implied probability and built-in vigorish (vig) behind every line.
Whether you're comparing odds across sportsbooks, evaluating the fairness of a line, or calculating potential payouts, this calculator provides all the conversions and analytics you need. Understanding implied probability versus your own assessment of a fight is the foundation of finding value in combat sports odds.
This tool works for any combat sport—UFC, boxing, kickboxing, Muay Thai—since odds formats are universal across all fighting disciplines. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation. By automating the calculation, you save time and reduce the risk of costly errors in your planning and decision-making process.
Different sportsbooks and regions use different odds formats. American odds are standard in the US, decimal odds dominate in Europe and Australia, and fractional odds are traditional in the UK. This calculator instantly converts between all three formats for both fighters, calculates implied probability with and without vig, and shows your potential payout on any wager amount.
American to Decimal: If American > 0: Decimal = (American ÷ 100) + 1. If American < 0: Decimal = (100 ÷ |American|) + 1. Decimal to Implied Probability: IP = (1 ÷ Decimal) × 100%. Vig = Total Implied Probability − 100%. Vig-Free Probability: True Prob = Raw IP ÷ Total IP × 100%.
Result: Fighter 1: -250 / 1.40 / 2/5 (71.43% implied). Fighter 2: +200 / 3.00 / 2/1 (33.33% implied). Vig: 4.76%
At -250 American odds, Fighter 1 has an implied probability of 71.43% (you'd need to bet $250 to win $100). At +200, Fighter 2 has a 33.33% implied probability ($100 bet wins $200). The combined implied probability is 104.76%, meaning there's a 4.76% vig. Vig-free probabilities are 68.18% and 31.82% respectively.
Different regions and sportsbooks use different odds formats. American moneyline is standard in the United States, decimal is used throughout Europe, Australia, and Canada, while fractional odds remain popular in the United Kingdom. Understanding all three formats helps you compare lines across international sportsbooks to find the best prices.
Every set of odds includes a built-in margin for the bookmaker called the vig or juice. A fair line for a 50/50 fight would be +100/+100 in American odds, but bookmakers typically offer -110/-110, creating about a 4.5% margin. In combat sports, the vig can range from 3% for major main events to 10%+ for smaller regional cards.
Comparing odds across multiple sportsbooks before placing a wager is crucial. Even small differences in odds can significantly impact long-term returns. Tools like this converter help you quickly evaluate whether the odds at different books represent fair value for the risk involved.
American odds use a base of $100. Negative odds (e.g., -250) show how much you must bet to win $100. Positive odds (e.g., +200) show how much you win on a $100 bet. A -250 favorite means you risk $250 to profit $100, while a +200 underdog means a $100 bet profits $200.
Decimal odds represent the total payout per $1 wagered, including your stake. For example, decimal odds of 3.00 mean you receive $3 for every $1 bet (your $1 stake plus $2 profit). Decimal odds always include 1.00 (your stake), so they're always greater than 1.
The vig (vigorish) or juice is the bookmaker's built-in profit margin. It's calculated as the total implied probability of all outcomes minus 100%. For example, if one fighter has 71.43% implied probability and the other 33.33%, the total is 104.76%, giving a vig of 4.76%.
Implied probability converts odds into a percentage that represents the bookmaker's assessment of each outcome's likelihood, including the vig. For decimal odds, it's simply 1 divided by the decimal odds, multiplied by 100. It helps you compare the bookmaker's view with your own assessment.
Fractional odds (e.g., 5/2) show profit relative to stake. Odds of 5/2 mean you profit $5 for every $2 wagered. They're traditional in UK and Irish betting. The first number is potential profit, the second is the stake required.
Value exists when you believe a fighter's true probability of winning is higher than the implied probability in the odds. For example, if the vig-free implied probability is 60% but you assess the fighter at 70%, that's a value opportunity. Consistent value identification requires deep fight analysis and understanding of the sport.