This guide is for anyone interested in sports betting online, from the casual punter to the serious, experienced sports bettor. It serves as an introduction to sport betting for novices, and as a guide to more in-depth sport bets for those with more experience.

This guide begins with an introduction to what sport betting is, before running through in detail various types of online bets. It then moves on to focus on individual sports, for example football betting, and the sort of bet that usually applies to them.

Betting odds are used by bookmakers to determine the likelihood of a given outcome in a sporting event. The odds quoted determine the probability of a particular outcome occurring in any sporting event. Betting odds also allow punters (the person making the bet) to determine the expected return on their stake should the predicted outcome become a reality.

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.


Probability reflects the likelihood of any given event happening. Betting odds are designed to do the same thing. The odds displayed on all sporting events on bookmaker site reflect the probability or ‘chances’ of each event they refer to happening.

An outcome at short odds is deemed very likely to happen, while those at longer odds are less likely to become true. Of course, it is important to point out that while probability in mathematics can be worked out scientifically, sport is something entirely different.

The reason we love to bet on sport is that the outcomes are not decided on any formula and the unpredictable nature of sport means that when you back something at long odds, it can still happen even if the odds are implying it is improbable. Equally, backing something at short odds with a potentially high probability does not guarantee it will become true.

As we have suggested, bookmakers use odds to display the probability or otherwise of all outcomes on sporting events. They can do this in one of three ways: fractional e.g. 2/1, decimal e.g. 3.00 or American e.g. +200.

Whenever you see two numbers separated by a slash, i.e. 4/1, this is a fractional betting odd. The number on the right is the unit stake you are betting in and the number on the left is the potential return per unit 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

Fractional Odds Equation

Decimals are an alternative to seeing betting odds in the fractional format. Which option to view odds in is a personal preference for customers. Here is the calculation for decimal odds:

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

Decimal Odds Equation

American odds display a positive or negative figure to indicate the likelihood of any given outcome. A negative number indicates a short price while a positive number indicates a longer price. These could be +300 or -200, for example. American odds format uses a baseline figure of £100 for calculation. For example:

-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)

Here is a handy resource for comparing and converting odds between the fractional and decimal betting formats:

Odds Against

Odds on



“Odds on” is the opposite of “odds against”. It means that the event is more likely to happen than not. This is expressed with the smaller number first e.g. one to four (1/4). This means the particular outcome in that event is four times as likely to happen as not happen.
For gambling purposes, “odds on” means that the amount you stand to win is less than the amount staked.
In this scenario, if you staked £40 you will ‘win’ £50 if you have predicted the correct outcome (£40 stake + £10 winnings = £50 total).

The odds percentage chart below will help you consider the chances of any given bet being successful at the odds you have taken:


When the probability that the event will not happen is greater than the probability that it will, then the odds are “against” that event happening. Odds of, for example, six to one (6/1) are therefore sometimes said to be “six to one against”. For gambling purposes, “odds against” means that the amount you stand to win is greater than the amount staked. In this scenario, if you stake £10 you will ‘win’ £70 if you have predicted the correct outcome (£10 stake returned + £60 winnings = £70 total).


If you have ever become frustrated when attempting to place a multiple bet online, then the chances are you have encountered what are known as related contingencies.

Basically, the notion of related contingencies stops the punter from placing a single bet on multiple outcomes where each outcome could be seen to have an effect on a future outcome in the same bet.

From a bookmaking point of view, this is not permitted as the odds you are striking on one event may be directly affected by the outcome of another.


Let us dig slightly deeper to explain what exactly might be considered a related contingencies bet.

As the term suggests, related refers to something that is connected in some way while contingency refers to something that will possibly happen in the future.

In betting, therefore, related contingency rules stop us from placing bets on events that are deemed likely to have a direct impact on each other.

This is why you will sometimes find that if you add multiple selections to your betting slip, you will note that the option of placing an accumulator, for example, on these selections is not available.

To help avoid coming across this when placing future bets, let’s take some related contingency examples to clarify what might fall into this category.


Football is one of the most popularsports to bet on and therefore it has a multitude of betting markets available. Not all of these individual markets can be combined in a single bet.

For example, you might try to bet on Real Madrid to win their Champions League quarter-final tie and also to win the competition outright. This bet would not be possible under the related contingency rules as the two outcomes are intrinsically linked.

Basically, if Real Madrid win the quarter-final, the odds on them going on to win the competition will be decreased accordingly. The odds of Real Madrid winning their quarter-final, or indeed losing, are factored into the outright price on them winning the tournament.

Similarly, in the Premier League, you could not place a single bet on Manchester United to beat Chelsea and Manchester United to win the league. By beating Chelsea, Manchester United have improved their chances of winning the league (gaining three points) and so this outcome has an effect on the bet you are attempting to strike.

Within a single match, there are also examples of related contingencies. If Celtic are playing Rangers, you could not place a single bet on Celtic to have a player sent off and Rangers to win the match. If Celtic lose a player, this is deemed to have an impact on Rangers’ chances of winning the game.

Similar rules cover individual goalscorers and match outcomes. You cannot, for example, bet on Cristiano Ronaldo to score first and double this up with Real Madrid to win their game, as the first outcome would greatly affect the chances of the second occurring.

You should, however, look for special markets such as win casts or anytime scorer and match result markets. These account for the impact of related contingencies and offer odds to reflect this and allow you to bet on such outcomes accordingly.


Related contingencies are quite common across all sports. Take a darts match between Phil Taylor and Michael van Gerwen for example.

You could not place a bet on van Gerwen to win the match and to score the most ton-plus finishes. By accruing more ton-plus finishes, van Gerwen is likely to enhance his chances of winning the match.

As with football betting, you should look for special markets in cases like this, where you will often find markets that offer – as an example – van Gerwen to win the match and score more ton-plus finishes, or Taylor to win the match and score the most 180s. These markets take account of the relationship between the individual outcomes concerned.

Another potential example of a related contingency would be in horse racing. For the Royal Ascot Festival, most bookmakers will offer markets on the leading trainer and leading jockey across the entire five-day meeting.

You could not combine a bet in these two markets on Aidan O’Brien to leading trainer and Ryan Moore to be leading jockey. As Moore rides horses for O’Brien, their success or failure is extremely likely to be linked together.