How Betting Odds Work
Bookies use betting odds to show the likelihood of a given outcome. This could be the chance of a team winning a match or a player winning an award.
Whether you’re analysing outright markets or live betting, it’s imperative you understand what odds are showing you.
Along with the implied probability of the odds, they also indicate the potential returns from a given wager.
Here are some of the key terms to note before starting to bet:
-
Stake – this is the amount you decide to wager on your bet.
-
Odds – this is the ‘price’ you agree to stake your bet at.
-
Payout – this shows the expected return on your bet, if you are successful
Betting Odds and Probability
A probability is the likelihood of a certain outcome. Betting odds aim to show the probability of a given outcome in a selected sporting event – this can be everything from Joe Root scoring a 50 to Harry Kane scoring two goals in a match.
It is possible to calculate the implied probability of an outcome using the betting odds published by a bookmaker. Bookies calculate the chance of an event happening to help them work out their odds.
An outcome at short odds will carry a higher implied probability, meaning it is much more likely to happen. Longer odds make an event less likely. In fractional odds, for instance, an event at 5/4 is far more likely than an event at 9/2.
Sports, by definition, are unpredictable. There are surprises at all levels of sport. Just because a horse is heavily favoured to win a race, there’s no guarantee it will do so.
The same goes for every sport – the challenge with predicting the outcome of sports betting markets is part of the reason online sports gambling has become so popular.
Bookmakers will use fractional, decimal, or American odds to display the implied probability of an outcome.
Fractional vs Decimal
Fractional Odds Explained
Fractional odds are presented with a slash between two numbers. The number on the right is the unit stake. The number on the left represents the potential winnings if you were to place that stake.
In the case of a 4/1 bet, your bet is £1 and if it is successful you will win £4. The total return on this bet would therefore be £5 (initial £1 stake plus £4 winnings).
The probability of a 4/1 chance winning is 20% - based on his calculation 1 / (4 + 1) = 0.20
Decimal Odds Explained
It is a matter of preference whether a bettor prefers decimal odds. As you might have guessed, these are demonstrated with a number given to two decimal places.
The calculation for decimal odds is as follows:
Winnings = (odds * stake) - stake
Decimal odds are written as 9.0 (which is the equivalent of 8/1 in fractional odds).
When you see decimal odds displayed, remember that these include your unit stake of one.
If you bet £1 at 9.0 and your bet wins, you will get back £9 (initial £1 stake plus £8 winnings). The probability of a 9.0 chance winning is 10% - based on this calculation 1 / (9 + 1) = 0.10
American Odds Explained
American odds are perhaps the most complicated. A number is given with a plus or minus in front of it. Wagers are odds-on if they have a minus, such as -200 or -500. Anything with a plus, like +500, is odds against.
The calculation is based off £100 as the stake. Unlike the presentation of fractional odds, this does not change.
Here are a couple of examples:
-
A -200 means you need to bet £200 to win £100. If your bet wins your return would be £300 (£200 stake plus £100 winnings).
-
A +300 means you have to bet £100 to win £300. If your bet wins the return would be £400 (£100 stake plus £300 winnings).
ODDS CONVERSION TABLE
Here is a handy resource for comparing and converting odds between the fractional and decimal betting formats:
Odds Against
| FRACTIONAL | DECIMAL | IMPLIED PROBABILITY |
| 1/1 | 2.0 | 50.0 |
| 21/20 | 2.05 | 48.8 |
| 11/10 | 2.1 | 47.6 |
| 6/5 | 2.2 | 45.5 |
| 5/4 | 2.25 | 44.4 |
| 13/10 | 2.3 | 43.5 |
| 11/8 | 2.375 | 42.1 |
| 7/5 | 2.4 | 41.7 |
| 6/4 | 2.5 | 40.0 |
| 8/5 | 2.6 | 38.5 |
| 13/8 | 2.625 | 38.1 |
| 17/10 | 2.7 | 37.0 |
| 7/4 | 2.75 | 36.4 |
| 9/5 | 2.8 | 35.7 |
| 15/8 | 2.875 | 34.8 |
| 19/10 | 2.9 | 34.5 |
| 2/1 | 3.00 | 33.3 |
| 21/10 | 3.1 | 32.3 |
| 11/5 | 3.2 | 31.3 |
| 9/4 | 3.25 | 30.8 |
| 23/10 | 3.25 | 30.3 |
| 12/5 | 3.4 | 29.4 |
| 5/2 | 3.5 | 28.6 |
| 15/5 | 3.6 | 25.0 |
| 11/4 | 3.75 | 26.7 |
| 14/5 | 3.8 | 26.3 |
| 3/1 | 4.00 | 25.0 |
| 16/5 | 4.2 | 23.8 |
| 10/3 | 4.333 | 23.1 |
| 7/2 | 4.5 | 22.2 |
| 18/5 | 4.6 | 21.7 |
| 4/1 | 5.00 | 20.0 |
| 9/2 | 5.5 | 18.2 |
| 5/1 | 6.0 | 16.7 |
| 11/2 | 6.5 | 15.4 |
| 6/1 | 7.0 | 14.3 |
| 13/2 | 7.5 | 13.3 |
| 7/1 | 8.0 | 12.5 |
| 15/2 | 8.5 | 11.8 |
| 8/1 | 9.0 | 11.1 |
| 17/2 | 9.5 | 10.2 |
| 9/1 | 10.0 | 10.0 |
| 10/1 | 11.00 | 9.1 |
| 16/1 | 17.00 | 5.9 |
| 33/1 | 34.00 | 2.9 |
| 50/1 | 51.00 | 2.0 |
Odds On
| FRACTIONAL | DECIMAL | IMPLIED PROBABILITY |
| 1/1 | 2.0 | 50.0 |
| 20/21 | 1.952 | 51.2 |
| 10/11 | 1.909 | 52.4 |
| 9/10 | 1.9 | 52.6 |
| 5/6 | 1.833 | 54.5 |
| 4/5 | 1.8 | 55.6 |
| 8/11 | 1.727 | 57.9 |
| 7/10 | 1.7 | 58.8 |
| 4/6 | 1.667 | 60.0 |
| 8/13 | 1.615 | 61.9 |
| 3/5 | 1.6 | 62.5 |
| 4/7 | 1.571 | 62.6 |
| 8/15 | 1.533 | 65.2 |
| 1/2 | 1.5 | 66.7 |
| 9/20 | 1.45 | 69.0 |
| 4/9 | 1.444 | 69.2 |
| 2/5 | 1.4 | 71.4 |
| 4/11 | 1.364 | 73.3 |
| 7/20 | 1.35 | 74.1 |
| 1/3 | 1.333 | 75.0 |
| 3/10 | 1.3 | 76.9 |
| 2/7 | 1.286 | 77.8 |
| 1/4 | 1.25 | 80.0 |
| 2/9 | 1.222 | 81.8 |
| 1/5 | 1.2 | 83.3 |
| 2/11 | 1.182 | 84.6 |
| 1/6 | 1.167 | 85.7 |
| 2/13 | 1.154 | 86.7 |
| 1/7 | 1.143 | 87.5 |
| 2/15 | 1.133 | 88.2 |
| 1/8 | 1.125 | 88.9 |
| 1/9 | 1.111 | 90.0 |
| 1/10 | 1.1 | 90.9 |
| 1/15 | 1.0667 | 93.8 |
| 1/20 | 1.05 | 95.2 |
| 1/100 | 1.01 | 99.0 |
ODDS ON VS ODDS AGAINST
Odds on simply means an event is more likely to happen than not. It is the opposition of odds against.
Any odds-on price carries an implied probability higher than 50%. Any odds-against price has an implied probability below 50%. A bet of exactly evens has an implied probability of 50%, and your winnings will be equal to your stake.
In fractional odds, an odds-on wager will see the smaller number on the left than the right. This is flipped for odds-against bets. For instance, 4/6 is an odds-on price with an implied probability of 60%.
Flip those odds to 6/4 and the implied probability drops to 40%.
When it comes to payouts, an odds-on bet simply means you will win less than you staked.
An odds-against wager means you will have larger potential winnings than you stake.
So if you placed £4 on England to beat France at 6/4, you would win £10 if the Three Lions were victorious.
| ODDS PERCENTAGE CHART | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
