Betting Odds Converter - American, Decimal & Fractional

FROM FORMAT

AMERICAN ODDS

Use a negative number for favorites (e.g. -150) and a positive number for underdogs (e.g. +200).

Implied Probability

60.0%

American-150

Decimal1.67

Fractional2/3

What is a Odds Converter?

The Betting Odds Converter converts a single set of odds between American, Decimal, and Fractional formats, and computes the implied probability of that outcome, all shown simultaneously. Select your source format, enter the odds, and instantly see the equivalent value in the other two formats plus the implied win probability.

Since different sportsbooks and regions default to different odds formats, this tool makes it easy to compare offers or simply understand odds shown in an unfamiliar format.

Why Use a Betting Odds Converter?

Manually converting between American, decimal, and fractional odds involves several different formulas depending on which direction you're converting and whether the American odds are positive or negative, easy to make a sign error or apply the wrong formula.

This calculator computes all three formats and the implied probability at once, from whichever format you have on hand, removing the need to memorize multiple conversion formulas.

Who Should Use This Calculator?

Sports bettors comparing odds across sportsbooks that display different formats (American, decimal, or fractional).

Bettors new to a region's format, for example, a UK bettor encountering American odds for the first time, or vice versa.

Fantasy sports and prediction market users who want to understand the implied probability behind a set of odds.

Anyone curious about how betting odds translate into an implied likelihood of an outcome.

What Insights Does This Calculator Give You?

Implied probability, the primary result, showing the bookmaker-implied likelihood of the outcome as a percentage, derived directly from the odds.

American odds, the moneyline format standard in the United States, shown with the correct positive/negative sign.

Decimal odds, the total-payout-per-stake format standard across most of Europe, Canada, and Australia.

Fractional odds, the profit-relative-to-stake format traditional in UK and Irish betting markets.

How to use this Odds Converter calculator

Select your source format, American, Decimal, or Fractional, using the format toggle.
Enter the odds in the fields shown for that format (a single number for American or Decimal, or a numerator/denominator pair for Fractional).
Read all three equivalent odds formats and the implied probability, updated instantly as you type.
Switch formats anytime to convert a different set of odds without losing your place.

Show formula & methodology ↓Show less ↑

Formula & Methodology

American to decimal (positive odds): Decimal = 1 + (American ÷ 100)

American to decimal (negative odds): Decimal = 1 + (100 ÷ |American|)

Decimal to American: if Decimal ≥ 2, American = (Decimal − 1) × 100; otherwise American = −100 ÷ (Decimal − 1)

Fractional to decimal: Decimal = 1 + (Numerator ÷ Denominator)

Implied probability: Implied Probability = (1 ÷ Decimal Odds) × 100

Worked example:

American odds = -150

Decimal = 1 + (100 ÷ 150) = 1.67

Implied Probability = (1 ÷ 1.67) × 100 = 60.0%

Fractional ≈ 2/3

Note: This calculator converts the odds you enter directly and does not remove the bookmaker's built-in margin (vig). For a look at how implied probability compares to actual historical performance, see the Winning Percentage Calculator.

Frequently Asked Questions

What are the three main betting odds formats?

American (moneyline) odds use positive numbers for underdogs (like +200) and negative numbers for favorites (like -150); Decimal odds express total payout per unit staked, including the stake (like 2.50); and Fractional odds express profit relative to stake as a ratio (like 5/2), the traditional format used in the UK and Ireland.

How do I read American odds?

A negative American odds number (like -150) tells you how much you need to stake to win $100 profit, while a positive number (like +200) tells you how much profit you'd make on a $100 stake, favorites always show negative odds and underdogs always show positive odds.

How do I read decimal odds?

Decimal odds show your total return per unit staked, including your original stake, odds of 2.50 mean a $1 bet returns $2.50 total ($1.50 profit plus your original $1 stake back), making decimal odds simple to use for direct payout calculation.

How do I read fractional odds?

Fractional odds (like 5/2) show profit relative to stake, read as 'you win the numerator for every denominator you stake', a 5/2 bet means you win $5 profit for every $2 wagered, not counting the return of your original stake.

What is implied probability and how is it calculated?

Implied probability is the bookmaker-implied likelihood of an outcome derived directly from the odds, calculated as 1 divided by the decimal odds, then converted to a percentage, for example, decimal odds of 2.00 imply exactly a 50% probability of that outcome occurring, according to the odds offered.

Why don't implied probabilities across all outcomes in a market add up to exactly 100%?

Bookmakers build in a margin (often called the 'vig' or 'overround') by setting odds so that the implied probabilities of all possible outcomes sum to slightly more than 100%, this built-in margin is how sportsbooks generate profit regardless of the actual outcome.

Why would I need to convert between odds formats?

Different sportsbooks, countries, and betting communities default to different odds formats, American odds are standard in the US, decimal odds are common in Europe, Canada, and Australia, and fractional odds are traditional in the UK, converting lets you compare value across books that display odds differently.

How is fractional odds converted to decimal in this calculator?

This calculator converts fractional odds to decimal by adding 1 to the fraction's value (numerator ÷ denominator), since decimal odds include the returned stake while fractional odds only express profit, for example, 5/2 (2.5 in profit terms) becomes 3.5 in decimal form.

Why might the converted fractional odds show a slightly different fraction than expected?

Since decimal and American odds can represent any real number, converting back to a clean fraction requires finding the closest simple fraction (using a bounded search up to a two-digit denominator), for odds that don't correspond to a common 'nice' fraction, the displayed result is the closest reasonable approximation rather than an exact traditional bookmaker fraction.

Does this calculator account for the bookmaker's built-in margin?

No, this calculator converts the odds you enter directly and computes the implied probability from those specific odds alone, without adjusting for the vig or attempting to calculate the 'true' no-vig probability across a full betting market.

Can I use this to compare odds across two different sportsbooks?

Yes, convert both sportsbooks' odds to the same format (decimal is often easiest for direct comparison) using this calculator, then compare which offers the higher payout or more favorable implied probability for the same bet.

How does implied probability relate to a team's winning percentage?

Implied probability from betting odds is a forward-looking, market-derived estimate for a single upcoming event, while [winning percentage](/winning-percentage-calculator/) is a backward-looking statistic based on completed games, bettors sometimes compare a team's historical winning percentage against the current implied probability to spot potential value.

Also known as

odds converteramerican to decimal odds calculatorfractional odds calculatorimplied probability calculator