Casino Odds, RTP, and House Edge Explained

Odds, RTP and the house edge are all fundamental aspects of casino gaming and they all relate to each other. If you don’t know what they mean and how they affect the games you pick and play then keep reading, because this guide was made for you!

Basic Definitions

  • Game odds: Odds reflect the chances of a certain outcome happening. These are represented as a fraction (i.e. 18-37) or as a percentage (i.e. 48.6%).
  • RTP: This stands for Return to Player. It is a percentage, representing how much of the total stakes a casino game returns on average.
  • House edge: This is the casino's advantage, present in all casino games. It varies depending on the game being played and the bet being made.

Betting On Black In Roulette

Using the example of a bet on black in Roulette, this image demonstrates how odds, RTP, and house edge all relate to one another. The same odds, RTP, and house edge are also present when betting on red, even, or odd.

odds house edge and rtp

Game Odds

oddsOdds express the probability of a certain outcome and work differently for each casino game. The idea behind odds is that in games of skill you can calculate the probability of certain outcomes in a game - as avid Poker fans know well - and therefore make the most likely to win move and directly influence the outcome of the gameplay.

When you play casino games of skill such as Blackjack or Craps in this way you can increase your odds of winning. This therefore decreases the chance of the house doing so as you are playing the optimal strategy, based on maths. Whilst not all casino games give you the chance to increase your odds of winning through strategy, as some are based on chance alone, you can still use odds to calculate the odds of an outcome and decide how you want to bet.

Applying Odds To A Game

In European Roulette, knowing the number of pockets on the wheel means you can calculate the probability of each outcome happening. Then you can use this information to work out what type of bet you want to make, one more likely to win or lose.

Take a single number bet for example. European Roulette wheels have 37 pockets, numbered from 0-36. If you bet on a single number, there is 1 outcome out of 37 that will result in a win for you.

Translated into odds, this is 2.7% or 36-1 (i.e. mathematically, for every 36 misses you get 1 hit).

However, even though the odds of winning your bet are 36-1, the House only pays out 35-1 (i.e. 35x your bet). This is where the house edge comes from.

Now imagine you bet on red. That means there are 18 numbers that will give you a win, and 19 that will not. The odds of each outcome are as follows:

  • Red: 37-18 or 48.6%
  • Black: 37-18 or 48.6%
  • Zero: 36-1 or 2.7%

The zero existing on the table means that red/black bets are not a 50/50 chance, as some believe. Hitting a zero means you lose your bet regardless of whether you voted for red or black. This is what give the house their edge in this situation.

House Edge

houseedgeAs we touched on above, all casino games favour the casino thanks to a mathematical advantage called the house edge. 

The house edge varies between each casino game, and often different bets will carry their own house edge (as in Roulette). To calculate the house edge percentage, you can subtract the odds of your bet winning from 100.

There's nothing you can do to eliminate the house edge, but you can minimise it by using optimal strategy.

How Is The House Edge Built-In?

This is achieved by the game paying slightly less than the true game odds (as in the single number bet example above) or by having game rules that benefit the house, as in Blackjack.

In Blackjack, the house wins when players bust. As the dealer plays their hand last, there's a chance that the dealer wins all bets without having to even play their hand and risk busting.

The RTP % of every online casino game is published, meaning the information is available that will help you decide on the best game to play. Here's our top 7 to get you started. 

What Are The Top 7 Casino Games With The Lowest House Edge?

This list assumes that you are playing optimal strategy or making the bets with the lowest house edge.

  1. Video Poker: 0.46% - when playing perfect strategy on Jacks or Better.
  2. Blackjack: 0.5% - when using basic Blackjack strategy with standard rules (8 decks, dealer stands on soft 17).
  3. Baccarat: 1.06% - when playing standard rules (8 decks and 5% commission on winning Banker bets)
  4. Craps: 1.36% - when making a Don't Come or Don't Pass Line bet.
  5. Pai Gow Poker: 2.69% - when using the Simple Dealer-Banker strategy.
  6. Roulette: 2.7% - when making a red/black/eve/odd bet on European Roulette table (with only one 0 pocket).
  7. Slots: variable, but usually between 2-4%.

The Difference Between Probability And Odds

In a nutshell, probability can extend beyond a single bet to a group of bets. In certain games with certain rules, this can improve your chances of coming away with a win by reducing the house edge.

Let's take Craps for example. This game is unique as there is a bet called 'Taking The Odds' (or just 'The Odds'), which has a 0% house edge - meaning there is a completely even chance that you will win or lose that bet, just like flipping a coin.

The catch is, in order to Take The Odds, you must already have made either a 'Pass Line' bet or a 'Don't Pass' bet. The house edge of these bets is 1.41% and 1.36% respectively.

Therefore, Taking The Odds will always involve some form of house edge even though the bet itself has none. But it does have the benefit of improving the house edge when combined with your original bet.

Combining the 1.41% house edge of the Pass Line bet with the 0% house edge of The Odds bet brings the total house edge down to approximately 0.7%. If the game offers 'Double Odds', where you can make an Odds bet with a value that is double that of your original bet, this reduces the house edge further to 0.6%.

This continues depending on the multiplication of Odds you're allowed to make (the house edge is approximately 0.2% at 10x Odds) - but never to 0%. So, if you only stick to Pass Line or Don’t Pass bets, and take full advantage of whatever Odds bets are offered, you can get the house edge in Craps very low.

RTP (Return To Player) Percentage

RTPInstead of talking about the house edge in games, often the term is flipped on its head to show the amount of total stakes a game returns to players over time, otherwise known as RTP - Return to Player. It’s most commonly talked about in terms of Slots, but you will also find that card and table games have published RTPs.

That said, RTP is most often used as an indication of how much a Slots game will pay back on average. As it takes the form of a percentage, you can simplify it by imagining betting £1 100 times.

For example, the RTP of Blackjack is 99.5% when played with perfect strategy, meaning you would be expected to end up with £99.50 remaining after betting £1 100 times. Obviously, this is purely based on mathematical probability and is in no way a guarantee.

House Edge and RTP: Two Sides of the Same Coin

RTP and the house edge are two sides of the same coin. As RTP reflects the amount of total stakes returned, it’s easy to calculate the average house edge or casino profit by simply subtracting the RTP from 100%.

For example, take Slots game Starburst, which has a theoretical RTP of 96.06%. 100-96.06 = 3.97, therefore the house edge is 3.97%.

RTP in Slots

Slots only gives you one option when making a bet (at least until you get into the bonus games) - the spin button. Each spin is individual, and the result random with no relation to previous spins.

Depending on the game you can increase your RTP by playing the maximum number of betlines with the maximum bet. For example, the game may offer a different jackpot depending on your bet size.

Whilst this improves your RTP in the long-term, it also increases your cost significantly.

Theoretical vs Actual RTP

Theoretical RTP is the published rate of RTP, but it is not guaranteed that you will have this result. In Slots, it's entirely possible to spend £100 and win £0, just as it's possible to spend £0.50 and win huge jackpots.

In games of pure chance like Slots, it depends solely on your luck during that playing session. Whilst for 'skill games' like Blackjack, you can use strategy to maximise your odds of winning.

So whilst actual and theoretical RTP may change as you play, depending on how you play the game, you can trust the published RTP to be true. Casino game RTPs are independently tested by games auditors like eCOGRA and iTech Labs. These companies use software to play the games billions of times in order to verify that the RTP is as advertised.

Maximise Your Chances of Winning

Now you know exactly how these 3 critical concepts affect the games you play and the outcomes you can use this knowledge to make better gaming choices.

  • Pick games and bets with the smallest house edge/highest RTPs as they payout the most on average.
  • Learn the rules and bets of the games you play before you bet to maximise your chances of winning.
  • If you are playing a game of skill find out more about playing strategies to increase your odds of winning.
  • Remember that the results of casino games are decided by a random number generator (RNG) - meaning regardless of past results, each outcome is completely random - so don’t chase losses.
  • Prepare yourself to play any casino game by familiarising yourself with our casino game guides.

And of course, our experts have found and reviewed all of the best UK online casinos for you to choose from - take your pick from the list below when you're ready to play!

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