Calculating the payout percentage on an older slot machine is realy quite simple. We'll look at a simple example. Let's say you have a machine with 3 reels, and 20 symbols on each reel. You would multiply 20 * 20 * 20 to receieve the number of possible combinations that could appear on the payline for one coin, which is 8,000. If the number of possible payouts for any one spin add up to 7200 coins, then you divide this by 8000 to receieve a payback percentage of 90%. In the long run, the slot machine will pay back 90% of the money put into it, leaving the operator with a 10% profit.

Unless you know the number of stops on each reel and the amount of payoff possibilities for any given spin, you will not be able to figure out payoff percentages using probability theory. Since you often see only a few symbols at a time, you have no way of counting the number of stops on each wheel in order to determine the proper variables to calculate the odds.

Payouts for modern slot machines, even those with wheels in brick and mortar casinos, are governed by random number generators. Because of this, there are few secrets or strategies for winning at slot machines. Unless you have a great friend on the inside, you'll never know what the actual odds are. You can imagine that higher payout machines will be placed strategically throughout the casino floor. Online casinos have increasingly relied on independent auditors to verify payout percentages. While these audits provide no real information concerning a single session of play, they can give you a ballpark figure. It is not unusual to see online slots payong back 96%.

Random number generators (RNGs) were used in brick and mortar casinos long before casino action began migrating to the web. A random number generator constantly cycles through numbers. These numbers correspond to symbols and payoffs. Your outcome is determined long before the reels stop. When the RNG is triggered, either by inserting a coin, pulling a handle, pushing a button, or clicking a mouse, you will receive the payout it has determined. The symbols are just for fun. The expected payouts will be determined by probablility theory. Each favorable outcome multiplied by the payoff for that outcome added to every other favorable outcome multiplied by the payoffs for each respective outcome should be divided by the total of all possible outcomes to calculate the payoff percentage.