The Science Behind Slots

Slots are arguably the most popular form of gambling in the casino world. Whether it’s playing free games on slot machines just for fun or trying to win an incredible jackpot that will change their life, people are drawn to the excellent perks that slots offer.

These games are also the most common, with estimates of around 200,000 slot machines located in Las Vegas alone. These exclude the incredible libraries of online casinos, which offer significantly more games than brick-and-mortar casinos. 

Despite slots being so common, many people may take these games’ inner workings for granted. It is easy to overlook the complexity of how a slot works and the science behind it when you see a win roll onto the screen. That being the case, we’ve delved into the science behind slot machines and are here to explain exactly how they work from start to finish. 

Operating Systems

The first thing behind every slot machine, whether online and stored on a server or in a physical case, is the operating system that runs it. This operating system is similar to the one that runs your home PC or smartphone.

While some casino games may use a dedicated operating system developed specifically for slot games, most use two systems that you’ll be familiar with: Windows or Linux.

These operating systems are responsible for running the machine (in the case of physical slots) or the server that the slots run on. They are the base where all other software gets installed, and nothing would function without them. 

Casino Management Systems

The next part that keeps slots running is the Casino Management System. There are two leading players in this arena, the IGT Advantage system and Oasis 360, which are predominantly used for physical casinos. Online casinos make use of systems like Konami SYNKROS CMS and CasinoTrac.

These systems manage all the slots on a casino floor or online library. They track expenses, profits, wins, playtime, and various other metrics that help casinos decide which games to keep due to popularity and which ones may need replacing. 

It is also the responsibility of CMS systems to ensure that all games are secure, operating fairly, and not being tampered with by players. This may sound like a massive undertaking, but the development of these systems has made them work almost flawlessly in the modern age. 

Game Software/Program

The actual science behind slots comes from the game software, also called the game program or application. These programs are the actual coding for each game and thus control what the slot looks like, what sounds it plays, and how it operates. It also runs the most vital things behind any slot: the RNG (random number generator) and RTP (return to player). 

This framework is necessary to ensure slots, like any great game, run smoothly. Without it, the game would be a mass of symbols on the screen that don’t resemble anything close to a slot. 

Return to Player

One of the core elements of a slot machine is its RTP percentage. This value depicts how much of the money taken in by the machine is returned to players. For example, if a slot machine with an RTP of 95% takes in $10,000, $9,500 of that money will be returned to players as winnings. The other $500 will be taken by the casino in profits. This amount is called the house edge. 

While the RTP isn’t what drives the slot and decides who wins and who loses, it is vital information that works with the RNG to determine how often random spins should win. It is also a complex piece of mathematics because the RTP of slots (particularly online slots) isn’t always a constant. 

Online slots usually have an advertised RTP. This rate is usually the highest return to player that one can achieve while playing. However, this can only be achieved in some cases if you play on maximum bet. If you’re playing on a regular or lower bet, your RTP is lower. Because of this, the game software needs to recalculate its RTP constantly. 

Random Number Generator

You may have previously heard the saying that nothing in life is random. Well, the job of the random number generator (also called the pseudo-random number generator) is where the real science behind a slot machine comes in. It is responsible for making the impossible possible and randomizing slots and wins to deflect any chance of somebody discovering a pattern in spin results. 

While it may be hard to imagine that a computer or program—inherently designed to do what it is told—can create something random, RNGs do precisely this. Using specific parameters like the RTP of a game, possible winning combinations, and the concept of probability, RNGs are designed to ensure that there is no pattern to how a slot determines the next spin.

To do this, RNGs function on something called a game cycle. This cycle determines all possible combinations of wins on a slot. It then ensures that for every game cycle the results differ from the previous cycle. Sometimes, the same combination can occur more than once in a single cycle. 

Doing this allows a slot to be random and prevents anybody from being able to calculate what the following combination will be. Most slots recalculate the mathematics in a game cycle or RNG every 50 milliseconds to make them even more random. Recalculating happens whether you’re playing or not. 


While much more can be said about the science and intense maths behind slots, these step into the territory of needing a master’s degree in mathematics. However, knowing that slots operate using various systems working behind the scenes to ensure that play is fair may give you a greater appreciation of a simple spin and the calculations behind what made it possible. 

Nakoa Davis