What is Chance?

Betting School ImageOutside of gambling, chance is more commonly referred to in percentage terms. If you toss a coin then there is a 50% chance of it landing on heads and a 50% chance of tails. All possible outcomes in any event will add up to 100% .

If you roll a 6 sided dice, there is a one in six chance of any one number coming up. This can be expressed 16.66% (six possibilities divided by 100%).

Understanding Odds

Odds are simply a reflection of the chance or probability of a certain outcome in an event. In any event, every outcome has a chance or likelihood of taking place. Odds are simply an interpretation of those chances. The bookmakers form odds or prices to reflect those chances.

Most online bookmakers give you the option of which type of odds you want to use.

Decimal Odds Explained

Rather than using percentages, bookmakers use odds. Decimal odds are commonly used in Europe and also known as European odds.

To convert chances into decimal odds just take the chance as a % and divide into 100.

100%Chance = odds

So if you think something has a 20% chance of winning then 100/20 = 5


Say you wish to place a bet on an event which has decimal odds of 5.0. If you win, for every one pound you stake you will receive 5 pounds back. Stake £10 and you will receive back £50. You can see that your stake is included in the odds. European odds multiplied by your stake equals the payout. The odds show how many units the bookmaker pays out per unit staked.

Guide To Fractional Odds

The more traditional fractional odds are often used in the UK. Using the 20% chance example again, the factional odds are 4/1. Fractional odds are saying that for every 1 time you win then 4 times you will lose. Which is the same as saying you have a 20% chance of winning and an 80% chance of losing.


Say you wish to place a bet on an event which has odds of 4/1. If you win, for every pound you stake you will win £4 and you will receive your one pound stake back, giving you a total return of 5. If you place a bet of £10 at 4/1, then you will win £40 and have your £10 stake returned, giving a total return of £50. UK odds multiplied with your stake equals the winnings. The odds show how many units you win in terms of winning per unit staked.

US Odds

If you wish to bet on US Sports then you will also need to understand American odds. American odds are also known as lines or money line odds. If US Odds are indicated with a + sign then they show the amount you would win for a 100 stake. If there is a - sign then they show how much you need to stake to win 100.


So if you are betting on an event which has decimal odds of 5, or fractional odds of 4/1, the US Odds would be +400. If you are betting at decimal odds of 1.5, or fractional odds of 1/2, then the US odds would be -200US odds can be divided into positive odds and negative odds.

Negative US odds show how big a stake is needed for a winning of 100 units. Positive odds show how big your winnings are if you bet 100 units.

Relationship between Percentage Chance, Decimal, Fractional and US Odds The tool "What are the Odds" below shows you how percentage chance, decimal odds, fractional odds and US odds are expressed to mean the same thing!

Chance v Odds

Select a chance of winning below and see how this translates into the Fractional, Decimal and American odds

Chance of Winning
English Odds
European Odds
American Odds

Do You Understand Betting Odds Now?

Take the Exam on the right to make sure. All the exams you pass get added to your profile so everyone can see how knowledgeable you are. If you feel as though you need more help on this subject why not check out this blog which explains betting odds, bookie overrounds and plenty more from Man O Bong.

Gambling 'Odds Terms' Explained

Fixed Odds Betting

When you place a fixed odds bet, you are staking a certain fixed amount of money against the bookmakers money to predict the outcome of the event. The bookmakers odds reflect how much you will win from the bookmaker if your prediction is correct.


When placing a bet, your stake is the amount of money which you risk or gamble. If you win then your winnings are calculated according to the odds at which your bet was agreed.

Laying Odds

This is another term for a bookmaker taking bets. By agreeing your bet, the bookmaker is laying that particular outcome of the event. The bookmaker is risking their money to lay, or to promise to pay the winnings, should your bet be successful.

Odds Against

Odds against is the term used to describe a bet where you will receive a return of more than double your stake. The profit on the bet will be more than your stake.

Even Money

Also known as EVS, this is when the return will be double your stake. The profit on your bet will be the same as the amount you staked. Both you and the bookmaker are risking the same amount on the bet.

Odds On

Odds on is the term used to describe a bet where you will need to stake more than you will win, In fractional terms this is anything with odds of less than EVS, so 1/2 is odds on. The word 'on' indicates that the odds are reversed. You may hear the expression 2/1 on referring to a selection with odds of 1-2.

Short Odds

This indicates that a selection has a good chance of winning. Short odds will be where you wouldn't receive a large return for your investment. For example a horse at 6/4 would be considered short odds.

Long Odds

This indicates that a selection has a poor chance of winning. If you bet at long odds you will receive a good return on your investment if you are correct. For example, a horse at 50/1 would be considered Long Odds.

For explanations of other terms see our Betting Terminology A-Z guide.