Perhaps one of the most misunderstood topics in the world of online casino (not just online), this can cause quite a bit of confusion among a number of players of different levels of experience.

It is sometimes hard for gamblers to fathom, the extreme levels of mathematical application that goes into developing slots in terms of complex algorithms, formulas and equations for every kind of outcome.

The return to player element in the world of gambling is just one of a number of highly important factors behind the science of slots and how they operate. For professional gamblers, this forms part of their decision making process in relation to the different type of slots that they choose to play.

Return to Player (RTP) Guide

So, what exactly is return to player?

The return to player refers to the term that casinos (and online casinos) use to describe the exact percentage of all of the money that has been wagered that a slot machine will pay back to players over time. For example, when taking into account the averages dictated by the mathematics, if you make 100 £1 bets on a slot where the return to player rate is 95 percent, then you can expect to get £95 back in wins, though the house advantage and the return to player are both calculated with the long term in mind.

It is important to note however, that the average RTP of slots, is usually calculated over a key amount of game plays and not every time that a slot is played. As a result, the average RTP is usually measured and calculated between 10,000 and 100,000 or more for compensated and random machines respectively, depending on which category that they fall into.

Compensated machines: A compensated machine varies the chance of winning a prize as a result of what happened during the last play. When an instance occurs where the machine is below its target return to player percentage, then it may become significantly more generous, depending on a number of variables such as design, however the distribution of prizes is still considerably variable, being determined at random.

Random machines: A random machine relies solely on statistical probabilities in order for them to achieve their return to player target percentage. As a result, this means that the odds getting a win stay constant with previous wins or losses not affecting them in any way.

In the short term however, which refers to a large majority of gamblers, anything can happen so you should never wager more than you know that you can afford to lose. Generally, slots carry a return to player rate of between 90 percent and 97 percent, with most of them falling somewhere in the middle.

Essentially, the return to player percentage is a theoretical statistical calculation based on formulaic equations and should not really be taken too seriously.


Return to Player – the other side of the House Edge

Another way of thinking about return to player in slots, is that it is the opposite of the house edge. The way to understand this is, if a slot has a return to player rate of 95 percent, then the house edge is 5 percent.

Effectively the house edge is the mathematical advantage that the slot game has over you as you play over a period of time. From a player’s perspective, it is a good way of being able to tell which games are going to be the most profitable.

With table games, such as roulette the majority of players find it easier to be able to get a better understanding of how the house edge works, due to the fact that you have a better visual of what is happening, compared to slots because the mechanics of these are slightly more technical.


Correlation between Return to Player and win frequency

In some respect, return to player can be slightly misleading for players, because a game’s return to player rate does not give you any kind of indication of how often that you can expect to win.

As an illustration, some slots with a return to player rate of 96 percent may only have a successful winning combination of a payout that it is one in every 12 spins on average, while others may have a winning combination rate of one in every four spins on average.

This means that there is the potential catch is that slots with a higher win frequency might pay out more often, though only in smaller amounts, while slots which have a lower win frequency are more likely to pay out in larger amounts though only once over a longer period of time.


How to know whether payouts are both random and fair

This was perhaps a game changer for slot games. When attempting to try to form a clear picture and understanding of the maths and statistics it is crucial to realise that the numbers are based on 10s of thousands of events.

The key part to remember is that any outcome is subject to chance, because every slot has a random number generator (RNG) which means that every outcome is the result of chance, ensuring that it is kept completely unbiased.

Slot machines are programmed to not have any kind of memory. Some people might say that online slots will pay out regularly, however, they do not know when the last time you won was and for that matter, how much you won. Every spin that you make is completely individual, so even if you have just hit it big and won the jackpot, in theory you can still win a big amount on your next spin. Thanks to random number generators, every time you play a game, your chances of winning are exactly the same.


Slots which have a high return to player rate

Ultimately, if you are a slot playing enthusiast, it is always worth choosing the ones with a higher return to player percentage. As such, there are a number of slots that you can choose from which may just increase your gameplay experience.

Jack Hammer 2: This highly engaging slot from NetEnt has a theme based on crime and adventure and focuses on one exception to the rule; crime can pay! With a stellar 99 bet lines, which provide ample opportunities to win, this is married with the fact that the slot also carries a 97.1 percent return to player rate. The free spin feature on the slot means that you get an impressive 20 free plays where every win is doubled with extra wilds randomly landing on the reels.

Retro Reels Extreme Heat: One of the most popular slots in giant developer Microgaming’s portfolio, this has a classic feel to it with all of the symbols that you would expect to see on a retro slot machine, with cherries, lemons, bars and bells. The free spin bonus gives players 20 free plays with all wins doubled, while it also has a very novel respin feature. To top it all, the return to player rate is an impressive 97.5 percent.

Kings of Chicago: A video slot with some of the best elements of the classic poker game, this NetEnt offering has a return to player rate of 97.8 percent. Compared to normal slots where you get payouts for symbols that match across paylines, the way you win is that if you get a poker hand on one of the five paylines.

StarMania: Set against an outer space backdrop, this visually engaging slot has a 97.87 percent return to player rate. Comprising of 10 paylines with wins paid in both directions, every win line enables you the opportunity to gamble your prize in order to achieve double or even quadruple you win. Packed with great graphics and an abundance of features, this high return to player rate slot has been well developed.

Uncharted Seas: Set against a medieval style map, this visually stunning slot featuring a medley of sea creatures, plus symbols which include sun, moon and stars, this slot developed by Thunderkick has an array of attractive features. The free spins bonus offers 50 free plays to take advantage of the impressive 98.6 percent return to player rate.

Mega Joker: From one of the industry leading slot developers, NetEnt, this exciting slot features a return to player rate of up to 99 percent. The supermeter mode unlocks the 99 percent return to player rate, which means essentially that you can increase your max bet in order to try and capitalise on winning bigger amounts.


Final thoughts

While it is worth having an understanding of return to player rates when playing slots and how it works, if you overthink it too much it can take away from the enjoyment of playing slots.

Choosing slots which have a higher return to player rate generally makes sense, however always bear in mind that this number is generated based on thousands of plays and doesn’t necessarily apply directly to you. Ultimately, when playing slots, anything can happen and it is always worth setting a limit to your gameplay and never wager more than you can afford to lose.

Charles Baxendale

A keen researcher in the development of methods and theories for computer sciences. A lover of algorithms and mathematical computation. Consultant to online slots software companies and a player in my spare time.