What the House Percentage Means,
by Andy Glazer

Everyone understands that casinos are in business to make money, and they wouldn't put slots out onto the casino floors unless they made money. So it's pretty simple to see that slot machines take in more money than they pay out. Everyone just hopes that it's the other guy's money that goes in, and their money that gets paid out.

Just how much money goes in and stays in is determined, over the long haul, by the slot's RNG (random number generator). When a casino orders a particular slot machine, usually it can order it with an RNG set to return a precise percentage. «Send us a Red, White and Blue that returns 92%,» asks the slot manager, and that's what gets delivered.

What does 92% return mean? At one level, it seems simple: over the long run, for every dollar (or four quarters, or 20 nickels) that gets put into the machine, the machine will pay back to customers 92ў.

The two most important words in that last sentence are «long run.» In the short run, almost anything can happen. You can put in 20 nickels, one at a time, and lose every single time. You can put in 20 nickels, one at a time, and win every single time. Long run percentages are LONG. Sometimes it takes a machine months or even years for the percentage to conform to expectations.

One important thing to understand is that a machine has no way of «knowing» whether it is conforming to its programmed expectations. A 92% return machine has no way to realize that it has been paying back 95% since it was installed and so now it «needs to» start paying less, and no way to know that it has only been paying back 85% and so «has to» start paying back more.

This is important because I have heard of «system» players who got the bright idea to try to bribe casino officials to find out which machines had been paying back below expectations, reasoning that these machines were now «due.» Bad idea. This reasoning is similar to someone who takes a nice, shiny, freshly-minted quarter, flips it 20 times, and after seeing it come up Heads 15 times and Tails 5 times, tries to take the quarter around to friends and bet that the coin, when flipped, will come up Tails, because he knows the coin is «overdue. «

Over several thousand more trials, it is likely that the percentage of Tails flips will certainly increase, but that's just because a fair coin will come up Tails 50% of the time. The most likely result for that coin after another 980 flips is something very close to a total of 505 Heads, 495 Tails-exactly the amount the coin was trailing by after 20 flips. So don't depend on some mythical «law of averages» to help you beat the system.

So what should you expect, if you spend a weekend playing a 92% slot machine? If you bring $300 to play with (that is, bring a bankroll of $300), should you expect, with average luck, to lose $24?

No, you shouldn't, and this is one of the most important concepts to understand about slot play. How much you are gambling is a function of four factors:

  1. What denomination machine you are playing (i.e., a quarter machine or a dollar machine); and
  2. How many coins you play each spin; and
  3. How many times you spin the reels each hour; and
  4. How many hours you play in the course of your trip.

In other words, if you play a dollar slot, playing three coins each spin, and you spin the reels 200 times an hour, you are putting $600 into that machine every hour. If you play ten hours a day, for two days, you are putting $12,000 into that machine.

«Now hold the phone», you say. «I've played dollar slots for that much time, and I sure didn't bring any $12,000 with me. Something is wrong.»

Nothing is wrong. The numbers are right. What happened is that you don't lose every time you pull the handle. You won on a lot of pulls, sometimes quite a bit. So money goes in, and it comes back out again, so you have a chance to reinvest, or recycle, your winnings.

So if you bring $300, and start playing that 92% return dollar slot at three bucks a shot, you know that you can pull the handle at least 100 times, and if you have average luck, you would be down about $24 (it's actually extremely unlikely that you would be down exactly that amount, but it's a useful figure for learning how recycled slot money works). So you'd now have $276, and could pull the handle another 92 times, at which point, with average luck, you'd have lost roughly another $22, leaving you with $254… enough to pull the handle about another 85 times… and so on, and so on.

Even though you only brought $300, you're giving the casino much more than $300 worth of action. Because you don't lose every time, the money gets to go through the machine many times, with the casino taking its 8% nibble every time.

Remember, your actual results aren't going to look like this. Maybe after the first hundred pulls, you're winning $700, maybe you're losing $200. In the short run, anything can happen. But the more hours you spend at the machine, the more likely it is that your long-term results will start to resemble what's supposed to happen.

Because the casino figures to take a small bite out of your bankroll every time they get a shot at it, the faster you play, the faster you rate to lose. Someone who spins the reels 600 times an hour will, all else equal, lose about three times as fast as someone who spins the reels 200 times an hour.

As a result, unless you clearly know yourself to be someone who does not enjoy himself unless the reels are virtually never stopped, one of the smartest things you can do as a slot player is to SLOW DOWN.

Most people who enjoy slots would have a lot more fun playing eight hours a day at 200 spins an hour than they would playing two hours a day at 800 spins an hour-and the expected mathematical result is exactly the same.

The casino controls the pace of most of the games under its roof. Slots are one of the few exceptions, a game where YOU get to determine the pace. A smart player will play only as fast as he or she must to still enjoy the game. Anything faster is playing right into the casino's hands.

Andrew N.S. ( «Andy») Glazer is a professional poker, backgammon and blackjack player, and an expert in virtually all forms of gambling.