By convention only a set of fractions are used in fractional odds betting markets. The set does not include exact mathematical equivalents to all possible decimal and American odds. We use the closet fraction that is used in betting markets.

• Positive odds - 100 divided by (the american odds plus 100), multiplied by 100 to give a percentage e.g. American odds of 150 = (100 / (150 + 100)). 100 = 40%. Negative odds - Firstly multiply the american.
• This calculator will convert 'odds of winning' for an event into a probability percentage chance of success. Odds, are given as (chances for success): (chances against success) or vice versa.

For example, the exact mathematical equivalent of decimal odds 30 is fractional odds 29/1. However 29/1 is not used in betting markets, instead 30/1 is used, so that is what appears in this converter.

Our betting trends, also known as public betting percentages, represent actual.

For an explanation of the odds types on this table see decimal, fractional and American odds. To find out what the numbers really represent see understand odds as probability with overround.

Calculator Use

Convert stated odds to a decimal value of probability and a percentage value of winning and losing. This calculator will convert 'odds for winning' an event or 'odds against winning' an event into percentage chances of both winning and losing.

Be careful if you are using sports teams odds or betting odds. If you see that the Patriots super bowl odds are 9/2, that is most likely 'odds against' and should be entered in the calculator with 'Odds are: against winning.'

When playing a lottery or other games of chance be sure you understand the odds or probability that is reported by the game organizer. A 1 in 500 chance of winning, or probability of winning, is entered into this calculator as '1 to 500 Odds are for winning'. You may also see odds reported simply as chance of winning as 500:1. This most likely means '500 to 1 Odds are against winning' which is exactly the same as '1 to 500 Odds are for winning.'

Probability Formulas:

This calculator will convert 'odds of winning' for an event into a probability percentage chance of success.

How To Calculate Odds Payout

Odds, are given as (chances for success) : (chances against success) or vice versa.

How To Convert Betting Odds To Percentages

If odds are stated as an A to B chance of winning then the probability of winning is given as P_W = A / (A + B) while the probability of losing is given as P_L = B / (A + B).

How To Turn Betting Odds Into Percentages

For example, you win a game if you pull an ace out of a full deck of 52 cards. Pulling any other card you lose. The chance of winning is 4 out of 52, while the chance against winning is 48 out of 52 (52-4=48). Entering A=4 and B=48 into the calculator as 4:48 odds are for winning you get

For 4 to 48 odds for winning;
Probability of:
Winning = (0.0769) or 7.6923%
Losing = (0.9231) or 92.3077%
'Odds for' winning: 1:12 (reduced from 4:48)
'Odds against' winning: 12:1 (reduced from 48:4)

Further Reading