Odds Probability Calculator
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."
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.
If odds are stated as an A to B chance of winning then the probability of winning is given as PW = A / (A + B) while the probability of losing is given as PL = B / (A + B).
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;
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)