Casino Odds: Overview

You will often hear the term 'Odds' mentioned when real-world or online casino betting is being discussed, so fully understanding what they actually represent and how that impacts on you as a player is knowledge well worth acquiring. It needs a little maths but, trust us, it's worth it!

Odds derive from the maths of probability and are measures of the statistical chance that an event will happen. For the purists amongst you, the strict mathematical calculation of an odd is done by dividing p (where p is the probability of the event happening) by 1, or more neatly p/(1-p).

To give this a little more clarity here's a practical example. A standard deck of cards has four Aces, so the Ace of Spades has a 1 in 4 chance that it will be the first of the Aces to be dealt from a freshly shuffled pack. That means the probability of this happening, p, is 0.25 i.e. 1÷4. Putting this into the equation above we can find the true odds –

0.25 / (1-0.25) = 0.25 / 0.75 = 0.33333333333 = 1/3

This would normally be expressed as 'odds' of 3 to 1 against. In betting terms that could translate to a bet of £1 on this event happening attracting a payout of £3 on top of that stake if the bet won.

Knowing how true odds are calculated is a vital part of understanding the concept of the house edge in casino gambling and how that can influence your betting choices.

The house edge (sometimes called the house advantage) is the calculation of the statistical advantage the casino has over a player for a specific bet over a long-term period. Put more simply it is the mechanism by which a casino earns its money, but that should not be interpreted as meaning the outcome is fixed against the player! The house edge is the measure of the degree to which the odds offered by a casino for a specified bet differs from the true odds of the event happening. An example should make things clearer:

The true odds of winning an Evens Bet (say, betting for black to win) on a European Roulette game is mathematically 1.056 to 1. Properly regulated casinos, including those UK online casinos we list on this site, will pay this as 1 to 1. This means the odds offered are marginally inferior to the true odds (and in this example the house edge is almost negligible!)

To put all of this into context, the bets that are most advantageous for the player in any casino are those that attract the lowest house edge, since the average theoretical loss per wager over a long-term period is lowest for those bets. It does not mean such bets are more likely to win, simply that the possible reward is more closely matched mathematically to the risk of the bet.