How Do Slot Machines Work?

Slot machines are easy to play. Simply put your money in, hit a button or pull a lever, and wait for the results. But most people don’t know how slot machines work beyond this.

The good news is, you don’t have to know how they work to play. But, if you want to learn how slots work we’ve put together all of the information you need.

Random Number Generator – RNG

The random number generator, or RNG, is the core of how modern slot machines work. The RNG is a computer program that does just what it says: generate random numbers.

Here’s an example:

Let’s start with a simple example to show how a random number generator works. If you wanted to use a computer to simulate a die roll for a six sided die you’d build an RNG with six possible outcomes, each with the same chance of being chosen.

The program has six numbers consisting of one, two, three, four, five, and six. The program cycles through these numbers at a high rate of speed.

When you click the button to generate a result, the program stops and displays the number currently at the top of the cycle. Most computer programs actually start with zero instead of one, so the program might use the numbers zero, one, two, three, four, and five. In this case, each of the numbers is paired with one of the numbers one through six on a normal die.

The pairing can be made in one of two ways. The first way is:

  • 0 = 1
  • 1 = 2
  • 2 = 3
  • 3 = 4
  • 4 = 5
  • 5 = 6

The second way is:

  • 1 = 1
  • 2 = 2
  • 3 = 3
  • 4 = 4
  • 5 = 5
  • 0 = 6

It doesn’t matter which method is used, because wherever the cycle stops the computer program takes the current number and displays the value associated with it. This is an important thing to understand because modern slot machines have many more possible outcomes.

In the example using a six sided die each possible result has the same chance to occur. Most modern slot machines are designed with multiple possible results with varying degrees of probability of being displayed.

This complicates things to some degree, but if the program is designed correctly it’s easy for the computer to quickly and accurately produce the desired results.

Here’s an example:

This is a more in depth example, but it’s still simpler than most modern slot machines. But if you understand this example, you understand how even the most complicated machine works.

A slot machine has a set jackpot that pays 500,000 times the amount wagered that hits on average one out of 1,000,000 spins. It’s designed to offer no pay out on 75% of the spins on average and pays back an amount equal to the bet on the spin 20% of the time.

It pays out twice the wagered amount 1% of the time, three times the wagered amount 1% of the time, four times the wagered amount 1% of the time, five times the wagered amount 1% of the time and 10 times the wagered amount 9,999 times out of 1,000,000 spins.

The base for the RNG is 1,000,000 numbers, or spots, because the lowest chance for a single outcome is the jackpot that is hit one out of 1,000,000 times. Once you know the base, the assignment of the rest of the numbers is simple.

Here are how many numbers are assigned to each possible outcome followed by an example of the actual numbers assigned on the RNG.

  • No payout is assigned to 750,000 numbers – Numbers one through 750,000.
  • A 1 to 1 payout is assigned to 200,000 numbers – Numbers 750,001through 950,000.
  • A 2 to 1 payout is assigned to 10,000 numbers – Numbers 950,001 through 960,000.
  • A 3 to 1 payout is assigned to 10,000 numbers – Numbers 960,001 through 970,000.
  • A 4 to 1 payout is assigned to 10,000 numbers – Numbers 970,001 through 980,000.
  • A 5 to 1 payout is assigned to 10,000 numbers – Numbers 980,001 through 990,000.
  • A 10 to 1 payout is assigned to 9,999 numbers – Numbers 990,001 through 999,999.
  • The jackpot is assigned to one number – Number 1,000,000 or zero.

Though this is a fictitious example, it’s realistic because it produces a slot machine with a 93.999 pay back percentage. This falls in line with a normal pay back percentage for a slot machine.

Now that you understand how the random number generator controls the slot machine and the payouts, it’s time to learn how this works with the rest of the machine to show you the action on the screen.

What’s Displayed on the Screen

Modern slot machines found in land based casinos operate the same as the ones you play online. They both use an RNG based program and display the results on a screen of some type. When you play in a casino the screen is part of the actual machine and when you play online the screen is your computer monitor, or tablet or phone screen.

The screen is simply a video demonstration for your enjoyment that displays the results created by the random number generator. This is usually shown in the form of spinning reels that form pay lines.

Once the RNG determines the outcome of the spin it creates the presentation on the screen. Some machines are designed so it looks like the reels landed just a fraction past making you a winner, but this isn’t what actually happened.

The end result is what you see on the screen is designed for entertainment and to keep you playing. The results are the same as they’d be if the screen simply showed how much you win or lose on each spin.

Frequently Asked Questions

Do Slot Machines Still Have Reels?

When you play online slots, all of the machines are computer based and don’t have actual reels. Most machines use reels on their displays, but the machines don’t really have them.

The same is true for most slot machines you play in land based casinos. The reels are displayed on a video screen or monitor, but the machine doesn’t actually include real reels.

A few older slot machines found in land based casinos have actual reels. But they’re becoming rarer all of the time.

Can You Clock or Game Modern RNG Based Slot Machines Using Timing?

The first thing many players ask once they learn how the RNG system works is if there’s any way to time their spins or clock them so they can win more. The random number generator and computer program run so fast that it’s impossible to get an advantage.

The RNG generates thousands of cycles per second so it’s impossible to track or act quick enough to alter the results. In addition, the computer program running the slot machine is designed to provide a set pay back percentage and a set house edge in the long run.

Now that you know how slot machines work, you can get back to enjoying your slots play knowing that nothing you can do alters the results.