Why Are + and – on Betting Odds?

When placing a wager on sports events, especially if the outcome’s likely to be in the contestants’ favour, you’ll often see the + and – next to the odds. What do these symbols mean? In this article, we’ll explore the origins of odds and where they come from, as well as how to read and use them correctly.


According to the Oxford English Dictionary, ‘odds’ is “the amount of money, or equivalently the bet, required to win (something)”. The definition includes both short-handed odds, e.g. “the odds of winning a race”, and long-handed odds, e.g. “the odds of rainfall at Metereor in the next twenty-four hours”. The latter are also referred to as the ‘full odds’.

The earliest record of the use of odds in relation to betting can be traced back to 1836 in England, where they were first used in a betting slip. But it wasn’t until the twentieth century that they became widely adopted across sportsbooks and casinos. In the UK, for example, they were used from the 1910s until the 1950s, when they were gradually phased out in favour of more abstract odds symbols such as “x” for evens and “o” for odds.

What Are The Origins Of Odds?

While there’s no exact record of when and where odds originated, it’s generally accepted that they come from a place with a very rich betting heritage: Ireland. In fact, the Irish word for ‘odds’ is ‘béaráid’, which literally means ‘bear arms’ (as in ‘castle defence’) due to the widespread practice of placing wagers on the outcome of battles between rival families or clans. This practice developed into a sort of sport in its own right and eventually led to the establishment of the Irish Jockey Club in 1889 – the same year that odds were first used in relation to sport in England. The English and Irish versions of odds later merged to form what we know today as ‘sports odds’.

Another possible source of odds is the French town of Nice. According to local folklore, a Nice native named Michel de Montaigne wrote the first ever book on ‘the science of betting’ in the 16th century. In it, he described a process of trial and error before a match, whereby a punter would wager on the outcome and then analyze the results to determine how much he should actually bet on the winning side. According to the Nice mayor’s office, locals still call their town ‘Montagne’ after this eccentric polymath. Perhaps the most likely source of odds, though, is from Barcelona, where a 17th-century book titled El Cocotiero Catalan offered suggestions on how to increase winning chances by using odds. This may have been the origin of professional punters hunching over a table with a pile of paper and pencils, ready to do their calculations as soon as the stumps are drawn in an England vs India cricket match.

Odds & Fixed Odds

Nowadays, when people think of betting odds, they usually think of them in relation to sports events. But they have much more widespread usage in other areas as well, such as horse racing. In particular, fixed odds betting (FOB) developed in the 19th century as a way of providing additional motivation for people to bet on certain outcomes. Basically, this is when a bookmaker sets the odds on an event before the start of the game. Those who back the sports teams/actors/commissions are encouraged to do so because the odds are often ‘fixed’ to be in their favour. This gives them a temporary edge in winning, although it can sometimes be difficult to assess how many points or dollars they should wager based on pre-game odds, as the game may end up being a draw. In that case, the bookmaker would have gained nothing. But people who bet on certain outcomes sometimes have an edge based on the fact that the odds were set in their favour beforehand – a practice still referred to as ‘value betting’ today.

How To Read & Use Odds

While it’s always best to consult a dictionary or thesaurus to confirm the correct meaning of a word or phrase, the only way to properly understand sports odds is by learning to read them correctly. Simply put, this means that you should learn to look at the odds on a betting slip, not at the letters + or – next to them. The OED also advises that you should “learn to appreciate that equivalencies exist between different measures of risk”, so even if you think that the favourite is ‘obviously’ the superior choice based on pure statistics, this may not be the case if they are both considered ‘risky’ bets. As with most things in life, there is no single ‘correct’ way to read or use odds – it’s a matter of personal preference.