Online slots articles 8

How Slot Machines Work

Mechanical Slots

The original mechanical slots had 3 spring mounted reels each with a number of symbols on them. There was an equal chance of any of the symbols coming up, and with a 20 symbol reel this would leave you with a 1/8,000 chance of a jackpot.

The 1970’s and 1980’s saw developments in terms of the number of reels on a slot machine and therefore the types of jackpots being paid out. The more reels on a machine, the lower the chance of hitting a jackpot are, and therefore the payouts are less frequent but higher. For example a 20 symbol 5 reel machine will only hit jackpot every 3,200,000 spins, approximately. These odds increase further with 7 or 8 reel machines, which have 1/1280,000,000 and 1/2, 5600, 000,000 chance of hitting their jackpots.

Video slots

The latest developments in the slot machine world came about with the video slot or virtual slot. Rather than physical reels with a limited number of symbols, a video slot will usually still have 3 or 5 reels (although 7 and even 10 do exist), but rather than 20 symbol possibilities, the video slot may have hundreds, enabling jackpots the size of the mechanical 7 or 8 reel slots, but without the clumsiness that has characterized those machines.

The virtual slots appear to have reels but in fact are operated by an RNG (random number generator). This system will produce results as randomly as a physical spin will whilst enabling a much larger number of possibilities than would ever be possible on a mechanical reel machine. On a 3 reel slot the RNG will pick 3 numbers randomly, the first will correspond to a position in the first of the three reels, the second to the second etc. The computer will then calculate the equivalent of this position on its imaginary reels, and direct the visual you see to spin to that outcome. The computer then checks if the ‘spin’ is a winner or not.


In terms of payment, each slot machine is set to its own payout percentage; this is a figure that can be decided upon by the machine administrator. This percentage is worked out as an average over an endless number of spins. This means that a 99% payout machine isn’t going to pay out 99% of what you put in it; rather, over its lifetime it will pay out 99% of what is put into it. Of equal importance in understanding how slot machines work is whether the machine is a high hit, or low hit machine. The ‘hit’ refers to hitting the jackpot. A machine that is programmed as a low hit machine will give large prizes rarely (low number of hits), whereas a high hit machine will pay out smaller amounts more regularly (high number of hits). Finally the widely held belief that winning on a slot machine is related to timing is false. Each spin is an individual occurrence, in no way related to what has come before.

Theo Evans