How to read betting odds: decimal, fractional, American

The rest of this page works through each format with a worked example, the conversion formulas between them, and a reference table checked cell by cell.

What decimal odds are

Decimal odds are the standard way most of the world prices a bet, and the simplest of the three formats to calculate with. The number is the total return per unit staked, including the stake itself.

The formula is total return equals stake multiplied by the decimal odds. Profit is the decimal odds minus 1, multiplied by the stake.

Worked example: at odds of 2.50, a 10 stake returns 25.00 in total (10 multiplied by 2.50). Profit is 15.00, since the original 10 stake is included in the 25.00 returned.

At odds of 3.00, a 10 stake returns 30.00, profit 20.00. At odds of 1.50, a 10 stake returns 15.00, profit 5.00. Decimal odds below 2.00 mean the potential profit is smaller than the stake, an odds-on price for the more likely outcome. Odds of exactly 2.00 return double the stake, and anything above 2.00 pays more than double.

What fractional odds are

Fractional odds are the traditional UK and Ireland format, written as two numbers separated by a slash, such as 3/2 or 5/1. Unlike decimal odds, a fractional price shows profit only, relative to the stake, not the total return.

The formula is profit equals the stake multiplied by the numerator divided by the denominator. Total return is the stake plus that profit.

Worked example: at 3/2, staking 2 wins 3 in profit, since 2 multiplied by 3/2 is 3. The total returned is 5, the 3 profit plus the original 2 stake back.

At 5/1, often read as "five to one", a 10 stake wins 50 profit, total return 60. At 1/2, an odds-on price, a 10 stake wins 5 profit, total return 15, since the profit here is smaller than the stake.

Converting decimal and fractional

To go from decimal to fractional, subtract 1 from the decimal odds, which isolates the profit per unit staked, then express that as a fraction in its simplest form.

Worked example: decimal 2.50 minus 1 is 1.50, which reduces to 3/2. So 2.50 decimal converts to 3/2 fractional.

Going the other way, from fractional to decimal, divide the numerator by the denominator, then add 1.

Worked example: 3/2 is 3 divided by 2, which is 1.50, plus 1 is 2.50. That confirms the conversion works both ways, 2.50 decimal and 3/2 fractional are the same price. A second check: decimal 3.00 minus 1 is 2.00, which is 2/1 fractional, and 2/1 is 2 divided by 1, plus 1, which is 3.00 again.

What American odds are

American odds, also called moneyline odds, are the standard format in the United States. They always carry a plus or minus sign, and the two signs work differently.

Positive American odds show the profit on a 100 stake. The American odds number itself is the profit on 100 staked, so +150 means a 100 stake wins 150 profit.

Negative American odds show the stake needed to win 100 profit. The absolute value of the American odds number is the stake required, so -200 means a 200 stake is needed to win 100 profit.

Positive American odds apply to prices longer than even money (decimal 2.00 or higher, the underdog side). Negative American odds apply to prices shorter than even money (decimal below 2.00, the favourite side).

Converting decimal and American

From decimal to American, the formula depends on whether the decimal odds are 2.00 or higher.

• If decimal odds are 2.00 or higher: American odds equal (decimal odds minus 1) multiplied by 100, shown as a positive number.
• If decimal odds are below 2.00: American odds equal -100 divided by (decimal odds minus 1), shown as a negative number.

Worked example: decimal 2.50 is 2.00 or higher, so American odds equal (2.50 minus 1) multiplied by 100, which is 1.50 multiplied by 100, giving +150. That matches the fractional conversion above, 2.50 decimal, 3/2 fractional and +150 American are the same price, checked three ways.

Worked example for a short price: decimal 1.50 is below 2.00, so American odds equal -100 divided by (1.50 minus 1), which is -100 divided by 0.50, giving -200.

Converting back from American to decimal also splits by sign. If American odds are positive, decimal odds equal (American odds divided by 100) plus 1. If American odds are negative, decimal odds equal (100 divided by the absolute value of the American odds) plus 1.

Worked example: +150 gives decimal odds of (150 divided by 100) plus 1, which is 1.50 plus 1, giving 2.50. And -200 gives decimal odds of (100 divided by 200) plus 1, which is 0.50 plus 1, giving 1.50. Both confirm the conversions above.

Conversion reference table

Every row below describes one price. Read across and each column shows the same price in a different format.

Every cell above was calculated from the formulas in this article and checked against FootyMetrics’ own odds conversion logic, the same code that powers the odds format setting used across the rest of the site.

Implied probability

Every odds format also implies a probability. From decimal odds, the formula is the simplest of the lot: implied probability equals 1 divided by the decimal odds.

Worked example: decimal 2.50 gives 1 divided by 2.50, which is 0.40, or 40%.

That raw number still has the bookmaker’s margin built into it, since a whole market’s implied probabilities always add up to a bit over 100%. Removing that margin to get to a true, no-vig probability is a bigger topic on its own, covered in full in What are fair odds and no-vig lines?, including the overround and how to devig a market.

Which format is used where

Decimal odds are the standard across most of Europe and are used on UK betting exchanges such as Betfair. A growing number of mainstream UK bookmakers now offer a decimal display too, though fractional remains the traditional and still widely used UK and Ireland format, especially in high street and racing contexts. American, or moneyline, odds are the standard in the United States and are what most US-facing sportsbooks show by default.