How Do Betting Odds Work?

If you’re keen to get into sports betting, odds are the first thing you’ll need to understand. Knowing what they mean and how to use them to your advantage is essential for having a fun betting experience. Betting odds show your chances of winning a bet, how much you stand to gain from a bet, and the bookmaker’s predictions for the match or event.

Depending on where you live, you’ll encounter odds displayed in one of three different ways, and we’ll show you how each one works. By the time you reach the end of this article, you’ll no longer be wondering: How do betting odds work? Instead, you’ll be looking for ways to cash in on your new knowledge.

The Power of Probability

Sports bookmakers anticipate the outcome of a match, event, or race using betting odds. They then offer those odds to bettors in the form of fractional, decimal, or moneyline odds. Specific types of odds are used in certain parts of the world, although the number of betting sites that allow you to switch between these types of odds is increasing. And if the site you’re on doesn’t allow this, you can use betting odds checkers to get all the info you need.

Bettors use odds both to estimate the probability of winning and determine how much cash they’ll gain from a successful bet. It doesn’t matter whether they’re soccer odds, horse riding, basketball, American football, or anything else; all sports odds follow similar patterns. Now let’s show you how to calculate betting odds.

Probability and Fractional Odds

Fractional odds are primarily used at the most significant betting sites in the UK and Ireland, and they’re reasonably simple to understand. They are represented with two numbers separated by a forward slash. Fractional odds are written as 3/1 and read as “three-to-one,” although some bookmakers write them as 3-1.

These betting odds can easily show you the probability of a specific sports outcome happening in the form of a percentage. The formula is as follows: probability percentage = B/(A+B), where A is the number on the left and B is the number on the right.

With the formula for fractional betting odds explained, let’s use the following example. Fractional odds of 5/1 have a 16.7% chance of happening, since 1/(5+1) gives 0.167, or 16.7%. Here are a couple more examples of the probability percentage in action.

  • 2/1 is 1/(2+1) = 0.33, or a 33% of a sports event happening.
  • 10/1 will give us 1/(10+1) = 0.09, or 9%.
  • 1/1 is calculated as 1(1+1) = 0.5, or 50%.
  • 1/2 is calculated as 2(1+2) = 0.67 or 67%.

Reading Fractional Odds

Fractional odds remain the most favoured betting odds in the UK and Ireland. They show you how much profit you gain if you win, along with the stake you have to put on the bet. As an example, 1/2 betting odds are called “odds-on” fractional odds, with the number on the right higher than the one on the left. This suggests that there’s a greater than 50% chance of the event happening.

In general, for fractional odds, the number on the left side of the forward slash is the potential profit if we stake the amount shown on the right side. 1/2 odds-on means it will return £3, with £1 in profit for every £2 stake.

Odds where the number on the left is higher than the one on the right are called “odds-against,” suggesting that the outcome is unlikely, and therefore more profitable if it does happen. 3/1 represents a bet that will return £4 with £3 profit for every £1 stake.

If you’re still wondering: “How do betting odds work in the UK?” here are a couple of examples:

  • 10/1 odds show that a successful bettor will get a return of £11 with £10 as profit for every £1 stake.
  • 7/2 means that for every successful £2 stake, you’ll win £7 in profit for a total return of £9. \
  • When you have a fractional odds of 1/1, these odds are called “even” and represent a 50/50 chance.

Crunching the Numbers with Decimal Odds

Decimal odds are used throughout Europe, Australia, Canada, and New Zealand. They’re probably the easiest betting odds to calculate, so the popularity of decimal odds is on the rise, with even some UK betting sites now using this format. So, how do these betting odds work?

Decimal odds show the total payout for every £1 you wager. The stake is the part of the decimal number, so there is no reason to add it separately. To calculate potential winnings, you simply multiply the odds and the stake.

For example, if you put a £1 bet on 2.00 decimal betting odds, you’d get a return of £2 if the outcome is favourable.

  • 10.00 – you’ll get £100 if you bet £10 on the right outcome.
  • 3.50 – If you stake £4, you’ll get a return of £14.
  • 1.25 – Bet £5 and if you’re right, you’ll get a return of £6.25.

To fully answer the question: “How do odds work in sports betting with the decimal system?” you need to keep one more thing in mind. You can also calculate probability using decimal odds by dividing one by the odds. This means the probability of 10.00 odds succeeding will be 0.1 or 10%.

  • 3.50 odds have a 28% chance of succeeding (1/3.50 = 0.28).
  • 1.25 odds have a probability of 80% (1/1.25 = 0.80).

If you’re in the UK, 10Bet reviews show that this sportsbook offers decimal odds.

American Odds

Moneyline is the odds system most used in the USA, especially with American football odds. If you see odds with a minus symbol, that represents how much cash you need to stake to win £100. Moneyline odds with a plus symbol show how much you’ll earn with a successful £100 bet.

Understanding betting odds can be especially tricky where moneyline is concerned. However, one of the most significant benefits of using the American odds system is that you can easily recognise the favourite and the underdog in a game.

Let’s consider these moneyline odds as a practical example:

Silver Orchid +150

Gold Dandelions -120

The plus symbol tells us that Silver Orchid is the underdog in this match. On the other hand, the minus symbol shows that Gold Dandelions are favourites here. For every successful £100 bet on Silver Orchid to win the game, you’ll get £150 in profit. If you put a £10 bet on Silver Orchid, you’ll earn £25 in total, with £15 in profit and your £10 stake returned.

Knowing how to read betting odds with moneyline largely depends on what sign is used before the number. If the Gold Dandelions win, for every £120 bet, a bettor would get £100 in profit. Place a successful £5 bet and you’ll receive £9.17 in total – with £4.17 in profit and a £5 stake.

There is a formula for calculating potential profit in a moneyline bet. For underdogs (with the plus symbol), the stake you put in is divided by 100, then multiplied by the odds. So, if Silver Orchid wins in our hypothetical situation, you get (£10/100 x 150), which equals £15 in profit. Add your £10 stake to this, and your total return will be £25.

Now let’s use the example of Gold Dandelions winning to get a better understanding of betting odds with moneyline. To calculate the favourite’s odds, you need to divide the stake by the odds then multiply by 100. So, if the Dandelions win, you’ll earn a profit of (£5/120 x 100) or £4.17. Add the £5 stake and you’ll get £9.17 in total.

Switching Between Fractional and Decimal Odds

Most betting sites offer multiple types of betting odds for you to choose from. However, if you still need to convert fractional odds to decimal on your own, here’s how to do it.

To turn 4/1 fractional odds into decimal odds, divide the number on the left side of the forward slash with the number on the right, then add one. In this case, we get 5.00. Below is the conversion of betting odds explained with a few more examples.

7/2 becomes 7/2 + 1 = 4.50 in decimal odds.

5/1 becomes 5/1 + 1 = 6.00 in decimal odds.

6/4 becomes 6/4 + 1 = 2.50 in decimal odds.

Don’t Fear the Odds

The earliest recorded usage of odds was in the 16th century, way before probability theory was even established. Horse racing odds have been used since the 17th century, and now they’re ubiquitous on horse racing betting sites. They are a powerful and essential tool in betting if you know how to use them. With the information gathered here, you’ll no longer have to ask: “How do odds work in betting?” Knowledge is the key, and now the only question is how far you’ll go.


What do odds of +200 mean?

These are American or moneyline odds. That means that for every £100 stake, the bettor will win £200 in profit if their choice wins. The plus symbol signifies that the chosen team is the underdog in a game.

How do you read betting odds?

It depends on what type of betting odds you’re reading. In the UK, the most popular are fractional odds, which look like 4/1, for example. If you place a £1 bet at these odds and win, you’ll get £5 in total: £4 in profit and £1 as your stake. When people ask: “How do betting odds work in football betting sites?” they’re usually referring to fractional odds.

What does +700 mean in odds?

Again, this is a moneyline bet. It means that for every £100 stake, the punter will win £700 in profit if successful for a whopping £800 in total earnings.

What does +800 mean in odds?

American odds use pluses and minuses to symbolise who is the underdog and who is the favourite in a match. In this case, if you place a £100 stake and the team you bet on wins, you’ll get £900 in total: £800 in profit, along with your £100 stake return. Please read our article entitled “How do betting odds work?” for more detailed information on how moneyline works.

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