How Slot Machines Work (and why the house always wins)


Unlike more so-called serious casino games like blackjack or poker, slots are simple and an easy, mindless diversion for those on the casino floor that want their entertainment without thinking too much about it. The result is self-evident; you do not need to be an expert in casino management to see how successful they have become. Nowadays, it is possible to play slots while you sip an ale at your favourite dive, or while you wait for your plane at the airport thanks to their ubiquitous installations in all manner of public establishments.

Even still, you can play from the throne in complete personal privacy due to the influx of apps that are clamouring for your attention, your addictive tendencies, and your money. It is no surprise that slot machines have expanded so rapidly to your favourite restaurant and personal device when reports started coming in that they were raking in some 60% of the annual gaming profits in the United States.

While the concept has grown wildly popular, and while the mechanical machines have been replaced by binary algorithms, the basic rules and game remains the same. And – spoiler alert – like the ironic tagline of the Hunger Games series, which features murderous and macabre blood sport, ‘May the odds ever be in your favour’ is not really what the house wants. The game is essentially one of probability, with just enough wins to make it attractive to continue playing, but carefully designed and tweaked so that if you play enough, you are very unlikely to come out on top. The only thing you may have to show for it, in fact, may be a gambling addiction.

Slot Machines:  The Design

Make no mistake, the odds are stacked against you. Even if you do end up with a relatively large payout, the casinos and designers of slot machine algorithms are banking on the player to reinvest those winnings into more games. Here is how it works: the player pulls a handle or presses a button, real or digital, to initiate the rotation of a series of wheels with pictures. You win by aligning the pictures in a specified order; there is a pay line that you can manipulate by placing a larger bet and increasing the total number of combinations to qualify for a winning condition. Depending on which pictures line up, you can win various rewards. With greater risk comes greater reward and a higher chance of winning.

Inside an antique mechanical slot machine.

Inside an antique mechanical slot machine. Source:

From Mechanical to Digital

No longer do machines operate on an elaborate scheme of gears and levers, but again, the basic idea has not changed, both for digital slot machines and online slots alike. Just like the older mechanical machines, the moment you pull the lever or press a button to start playing, the outcome is already determined whether you are playing a 3-reel single-line game or a 5-reel 25-line one.

But how random are the numbers, and what are the actual odds? According to the Nevada Gaming Control Board’s Gaming Revenue Report for December of 2012, there is an average win rate of 6.58% for slot machines during this fiscal year period. That rises to 10.77% for bets of one cent, and drops to 4.73% for bets of $100. In spite of the statistics for win rates that are available, the odds are not actually quantifiable because the design of the games remains a secret to the player.

This is unlike other poker games, where someone who is savvy enough in statistics can quickly calculate and play the odds depending on the situation. For this reason, even though the game is accessible and there is an ostensibly frequency of winning when you place small bets, beware that the addictive nature of the game is what entraps the player and ultimately ends up costing him or her.