Slot Machine Odds & Probability

When dealing with slot machines many players are curious about the probability of winning at slot games and how the odds work for the player.  It’s important to distinguish between the odds and probability of winning on any given pull and the overall payback percentage of a slot machine.  The payback percentage is expressed as the overall return that the machine pays out to the player over time, for example 97% would mean that the machine returns $97 for every $100 wagered over time.  This means that the casino house is guaranteed a profit of $3 on every $100 wagered over millions of spins of the reels.  Slot machine odds and probability on the other hand deal with the chances of winning a jackpot or hitting any of the pay lines on the reel.  This article deals with the latter and shows you how to figure out the chances of hitting a win on a given slot game.

The best way to look at and understand slot machine odds is to examine a typical 3 reel game which is usually comprised of three distinct reels and approximately 10 symbols on each of those reels.  Using this information, we can see that there is a 1 in 9 chance of hitting a specific symbol on a single reel, however we want to hit that symbol on more than one reel to ensure that we get paid out for that wager.  To calculate the probability of that happening, we need to divide the odds for each reel and multiply them by the chances of the same symbol coming up on all three reels on the machine.  For example the odds of hitting two of the same symbols with this layout would be 1/10 x 1/10 which would equal 1/100 or 99 to 1 in true odds form.  To hit three of the same symbols we would use the same formula and come to the value of 999 - 1 for hitting this particular combination.

This is the basic premise of how the actual chances of hitting a winning combination are calculated on a slot, but it’s important to note that these probabilities do not actually determine how often you will win since as you can see they are very unlikely to happen.  If you have ever played a slot machine, you will realize that it does not take 999 spins to hit three of the same symbols on one pay line, so why is this data used?  What you need to realize is that the actual payouts of each bet that you make on a slot are set way below the real probability of them occurring, however the payout of each winning bet is multiplied by the true probability to calculate the return and consequent monetary value that you will receive back for each spin.  When all of this data is added up for every single combination you will get the true payback percentage for that slot machine which is covered in another article on our site.

Still confused?  Let’s take a look at a real life example.  Say that on a 3 reel slot when you hit 3 cherries the payout is 10 coins, for simplicities sake each coin represents $1.  Now we know the chance of hitting these three symbols is 999 to 1, however the machine may be programmed to make this actually occur at a much more modest rate of 10 to 1 for example.  When this combination is hit, the machine will take into account the programmed and realistic probabilities for hitting that wager and then reward the player according to the payout table set for that specific machine.  By using this method of determining the payouts and probabilities, the casino is able to offer larger jackpots than simply giving the true odds to the player.

Another important consideration to understand with regards to payouts and probability is how they work with video slots online.  Since video slots can often times have 5 reels and literally hundreds of symbols, the casinos needed to be able to program certain combinations as less likely to hit than others.  The outcome of each game is still random, however certain winning combinations will not be hit as often as others, meaning the casino can use this to make jackpot wins scare which will increase both the value and likeliness of hitting a huge jackpot.  This may sound like a negative thing but is actually the only way casinos can offer such substantial slots payouts since if the symbols were not set to hit out less than others, than the amount of jackpots would be significantly reduced for players.

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