Home / Casino News And Tips / How A Slots Machine Allocates Free Spins
slot machine

How A Slots Machine Allocates Free Spins

A player by the name of ‘John’ asked us a very interesting slots question we’d like to share with you.

”I am curious how slot machines work, my friends tell me that they’re set up, but you guys keep on saying that they’re random. I know that you are experts and know what is really going on. Please explain to me how a slots decides how many free games you get once it’s triggered. I’d like to play a game that gives me 8, 10, 12, 15 or 20 free spins. Sometimes I get the smaller numbers and at times the big numbers. My friends never get the large numbers when they play that’s why they think the games are rigged. What’s really going on here?”

John, many thanks for contacting us. We don’t see ourselves as ‘experts’ just a bunch of dudes who enjoy playing slots. Any how we’ll try and answer your question as accurately as possible.

You are correct when you say that the free games are randomly allocated. If a slots’ bonus game awards a bunch of free spins, like you mention, then that selection is random. The slot machine’s program instructs its random number generator (RNG) to provide a random value which is converted into the amount of free spins you’ll get.

Here’s a peek behind the scenes as to how its created when the game is designed, produced and developed. A table of weights is set up by the game’s mathematician:

Award         Weight  Probability  Range of RNG
8 Free Spins    30        30%          1  – 30
10 Free Spins   25        25%          31 – 55
12 Free Spins   20        20%          56 – 70
15 Free Spins   15        15%          76 – 90
20 Free Spins   10        10%          91 – 100

Totals          100       100%         1 – 100

Have a look at the range of the ‘RNG’ column. It’s used at the beginning of the bonus game. Basically the program asks for a random number from 1 to 100. Based on the result (say 63) the game gives you the corresponding number of free games, 63 is in the range of 56 to 70, therefore the slots will award 12 free games.

If your friends don’t play the slot machine for a long session and only trigger a few bonus rounds, which number of free spins you think they’ll get? Based on the above table, 75% of the time they’ll receive 8, 10, or 12 free spins. Also, the probability of each reward is 30% + 25% + 20% = 75%. Before you play a slot machine determine if it’s a low, medium or high variance game – for what it’s worth we do mention each slots’ volatility in our reviews. The more volatile a game is the more spins is needed to initiate its free spins feature.

Each game provider allows you to play the game for ‘Free’ before you deposit real cash. Playing the game in the free mode gives you an idea about its game mechanic (how the slot pays at different coin levels), visual display, theme and how many spins is required (more or less) before a bonus round is triggered.

Another important thing to remember is to peruse the ‘Help Screen’ (Paytable) before you play. It tells you which symbols are the most valuable, the average return to player percentage (RTP) and how the in-play bonus rounds are triggered. If the game is fitted with a free spins feature it tells you the amount of scatters that’s needed to trigger the feature (3 or more scatters) and how many free spins is awarded by each scatter. For example, 3 scatters awards 10 free spins, 4 awards 15 and 5 awards 20 free spins. Some slots give you scatter pays with random/expanding wilds and multipliers of up to 15x.

In summary. Most players often get angry because they feel that the casino lies to them especially when it comes to random events. Although casinos state that there’s a 33.33% chance of winning a prize, players often claim that it’s more like one in twelve.

Keep in mind that the ‘chance of winning’ is merely an expression of probability based on the results of random events over the long-run and does not represent a guarantee. It’s like flipping a coin, there’s a one in two chance of getting heads or tails (50%) plus there’s no guarantee of either in the short term.

Further Reading

1. https://www.casinopedia.org/terms/f/free-spins