Odds Converted To Probability

by admin

Luckily, our odds converter does the hard work for you, so you don’t need to get your calculator out. However, if you’re interested in how the odds converter works, here’s a look at the maths behind it. Fractional and decimal odds. To convert fractional odds to decimal odds, you need to turn the fraction into decimal form and then add 1.

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.

  • The calculator will always display the implied probability of success that each set of odds represents. For example, +200 implies a probability of 33.33%, whereas -500 implies a probability of.
  • Have you ever wondered what the chances of a team winning was based off of the money line for the game? That’s a key part of understanding money line bets.First, we have a simple calculator that you can use to plug in any moneyline (American style odds) and quickly get the fair market probability.

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.

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

Odds

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;
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

If you can’t convert odds into the probabilities they imply, you are going to struggle in the long term to make money from your betting. How can you assess value if you don’t first know the probabilities the betting market is indicating?

It’s not a difficult thing to do and with a little practice you will be able to do it automatically every time you look at a betting market.

First we’ll look at conversion of fractional odds to probabilities as those are still the predominant type used in the UK.

Converting Fractional Odds

Fractional odds simply reflect the return you will get if your selection wins – bet £20 on a 4/1 shot and you’ll get £80 – 4 x £20 – back (plus your original stake of £20). However, they also reflect the bookmaker’s assessment of the chances of that selection winning . In addition, there’s an adjustment in there to cover the bookmaker’s profit margin (the overround) but for the purposes of this exercise we’ll ignore that.

So what percentage chance does the bookmaker think a selection has if he is offering 4/1? Here’s the calculation:

Divide the number on the right of the fraction by the total of both numbers in the fraction:

1 divided by (4+1) = 0.20

Then multiply that by 100 to give a percentage probability:

0.20 x 100 = 20%

So a 4/1 chance has an implied 20% chance of winning! Simples

Converting Decimal Odds

Again, like fractional, decimal odds are a reflection of the return you will receive if you win, including your stake. So if you have £20 on a winner with decimal odds of 7.0, you will receive £20 x 7 for a return, including stake, of £140 (£120 profit). To convert those odds into a probability, here’s the calculation:

Divide 1 by the decimal odds then multiply by 100 to give a percentage

1 divided by 7 = 0.143

Convert Odds Against To Probability

0.143 x 100 = 14.3%

So a selection priced at 7.0 in decimal format has an implied 14.3% chance of winning!

These are very simple calculations and with experience you will be able to look at a betting market and instantly calculate the implied winning chance of all the runners based on the odds on offer.

Vice Versa

If you have reached the point where you are compiling your own tissue prices as part of a value finding exercise (and that should be your aim!), you will need to be able to convert percentage probabilities back to odds format for the purpose of comparison.

Converting Probabilities to Fractional Odds

Based on your own assessment methods, you have determined that a horse has a 10% chance of winning a race. To convert that into fractional odds format the calculation is

(100 divided by percentage probability) -1

(100/10) -1

10-1 = 9

Convert Odds Ratio To Probability Stata

So a selection with a 10% chance of winning should be priced at 9/1

Converting Probabilities to Decimal Odds

In this example you’ve found a horse that you think has a 60% chance of winning it’s race. To calculate it’s odds in a decimal format:

Divide 100 by the percentage probability

100/60 = 1.66

So a 60% chance is expressed as 1.66 in decimal odds format.

Odds Converted To Probability Sampling

So there you have it. However, an even easier way to do it is to memorise the major odds and their respective implied probabilities using the table I have put together below!