Convert Odds To Probability

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?

Probability = 1/5 = 0.2; Out of 5 times, 1 time will be the event and 4 times will be the non-event, odds = 0.25. Odds = 1/5 / 4/5 = 1/4 = 0.25; Calculating the odds without the number of subjects: by the ratio of the number of events (1) by the number of non-events (4) odds = 1/4 = 0.25; Calculating Probability Given Odds. 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 that it implies. We’ve also included a chart below the calculator for reference, and to see how favorites and underdogs compare. Money Line Calculator (Implied Probability).

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

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

Converting Odds To Probability Equation

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

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

Converting Probabilities to Decimal Odds

Convert Odds To Probability Calculator

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.

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!

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 that it implies. We’ve also included a chart below the calculator for reference, and to see how favorites and underdogs compare.

Money Line Calculator (Implied Probability)

Convert Betting Odds To Probability

The following chart shows how likely a team is to win based off the odds. This is helpful in handicapping because you can see just what percentage of your wagers you need to win at each given money line in order to profit.

The left chart is to be used for favorites, the right for underdogs.

Convert Odds To Probability

Win % – Percentage of wins required to show a profit at a given money line.

Convert Odds To Probability Excel

For example, you would need to win 80% of all of your bets just to break even if you only bet on -400 money line favorites (over 80% to turn a profit).

Moneyline Conversion: Odds to Percentage Chart

Spread to Moneyline by Sport Conversion