Odds Calculator

Calculator for Sports Odds

Use our odds calculator to easily convert American (a.k.a. moneyline), Decimal, and fractional odds. You can also view corresponding odds by their implied probability of winning (expected win %), as well as calculate payouts for sports bets based on the amount wagered ($100.00 is used by default).

How to Use the Odds Calculator

Enter the odds in your preferred format and instantly view how they are converted into other popular types.  You may also manually adjust the bet amount in USD to calculate what your payout would be based on the odds provided.  Just hit the reset button if you’d like to start over.

Sports betting odds are usually displayed in one three formats: American, Decimal, and Fractional.

American Odds

These odds are often used in the United States and can be either positive or negative. If the odds are positive (+200), it signifies the amount you will win from a $100 bet. If the odds are negative (-200), it shows how much you need to bet to win $100.

Decimal Odds

This format is commonly used in Europe, Canada, and Australia. The odds represent the total return from a $1 bet. So, if the odds are 1.5, you would get $1.5 back for each $1 bet (including your original stake). They must be a number greater than 1.

Fractional Odds

Common in the UK and Ireland, these are expressed as fractions. For example, odds of 5/1 read as “five to one”, which means you would win $5 for every $1 bet.

Implied Probability

The odds reflect the bookmaker’s assessment of the implied probability of a particular outcome, not the actual probability. This is reflected as a percentage so the number will always be between 0% and 100%.  It also means what your break-even point for profitability is for those given odds.

Since not all sports betting sites use the same type by default, you can use this tool to quickly convert odds to a format that you understand.  You can also see the probability of winning that the oddsmaker implies by setting the line at what it is.  This is sometimes useful to help you understand what you are betting on.

This tool is for single wagers only.  Head to this link if you are looking for a parlay (multiple bet) calculator.

How to Calculate and Convert Odds

Our odds converter tool on this page is the best way to go between the different formats, but it’s also nice to know the math on how it works.

Guide to Converting Odds to a Probability Percentage


If you are going from decimal to implied probability percentage you simply divide 1 by the decimal odds then multiply the result by 100.

Here is an example using 2: (1/2)* 100 = 50%


When converting from American odds to a percentage you have a different formula if the number is positive or negative.  The positive you use (100 / (American odds + 100)) * 100.

So for example if you have +150 for then the formula would be (100 / (150+100)) * 100 = 40%.

On the other hand if you have a negative number you are trying to convert you start by multiplying the line by * -1 then dividing it by the positive number +100.

Here is the example for -150: ((-150 * -1) / ((-150*-1)+100)) * 100 = 60%

We also have an implied money line calculator you can use just for this.


And lastly for fractional you divide the denominator by the denominator plus the numerator and then multiply by 100.  The example would be 5/1: 1 / (5+1) *100  = 16.67%

How to Calculate American Odds

From Decimal

There are two different ways to convert from decimal to American odds.

If it’s greater than or equal to 2 you multiply the decimal odds minus one by 100.

Example for 2.1: (2.1 -1) * 100 = +110

On the other hand if it’s less than 2 you divide -100 by decimal odds minus one.

Example for 1.5: -100 / (1.5-1) = -200

From Fractional

There are two different methods.  If it’s over 1/1 you will divide the numerator by the denominator and multiply by 100.

Example of 7/2: (7/2) * 100 = +350

If it’s under 1/1 you divide -100 by the quotient of the numerator divided by the denominator.

Example of 1/5: -100 / (1/5) = -500

From Percentages

Like always with American odds you have different formulas for both positive and negative odds.  Positive numbers will be 50% and higher, negative numbers are below 50%.

With positive numbers you use 100 divided by the quotient of the percentage divided by 100, minus 100.

Example for 20%: 100 / (20/100) – 100 = +400

For negative lines it’s the probability divided by (one minus (the probability divided by 100)) then multiply by -1 to convert to a negative number.

Example for 60%: 60 / (1 – (60/100)) * -1 = -150

Converting Lines to Fractional Odds

From Decimal

Going from decimal to fractional odds is fairly straightforward.  You simply subtract one and convert it to a fraction.

Example of 3: 3-1 =2, which converts to 2/1

From American

You again have two different ways to convert American odds.  One for positive and one for negative.

For positive American numbers you divide the odds by 100 and then find the simplest form of the fraction.

Example of +300: 300/100 = 3/1

For negative numbers you divide -100 by the American odds.

Example of -300: -100 / -300 = 1/3

From Implied Percentages

Going to a fraction from a percentage is fairly easy.  You take one divided by the quotient of the percentage divided by 100 then subtract one.

Example of 20% = 1 /(20/100) -1 = 4/1

Converting to Decimal Odds

From American

To go from decimal to positive American odds you add one to the quotient of American odds divided by 100.

Example of +250: (250/100) + 1 = 2.5

If you are using a negative number then you subtract one from 100 divided by the American odds then multiplying by negative one.

Example of -250: (100/-250) -1 * -1 = 1.4

From Fractional

To go to decimal from fractional you divide the numerator by the denominator and add one.

Example for 3/2: 3/2 +1 = 2.5

Using Implied Percentages

You can take a percentage to decimal odds by one divided by the percentage divided by 100.

Example of 60%: 1 / (60/100) = 1.67

Hopefully understanding the different ways bookmakers use to display their lines will help you to spot value in the future.  Plus it might help to think in probabilities of winning instead of trying to find value with the lines displays.