By John Robison

Almost every casino has its own gaming guide, and every casino gaming guide I’ve ever read recommends playing full coin at all times on all slot machines. Many slot books make this same recommendation. The reason the books and guides give for always playing full coin is that you get the maximum long-term payback possible from a machine only when you play full coin. This statement is true for some machines. For others, it isn’t. Moreover concentrating only on long-term payback completely ignores the fact that you are putting more money at risk when you play full coin than when you play short coin. Is the extra risk always balanced out by the increase in payback?

Are you really better off playing full coin at all times on all machines? I analyzed the programming on over 1,000 slot machines to formulate Robison’s Rules for Playing Full Coin, which follow.

Play one coin at a time on Straight Multipliers.
A Straight Multiplier is a machine on which the payoffs for the winning combinations for the second coin are exactly twice those of the first coin, and the payoffs for the third coin are three times those of the first, etc. An example of a Straight Multiplier is a two-coin Double Diamond machine, which pays 800 coins for the jackpot when you play one coin, and 1,600 coins for the jackpot when you play two coins.

Playing more than one coin at a time on a Straight Multiplier is a waste of your bankroll. You’re not buying any new winning combinations, nor are you buying a bonus for a winning combination.
The long-term payback of a Straight Multiplier is the same regardless of how many coins you play. Let’s say you’re going to play 1,000 spins on a one-dollar two-coin Double Diamond machine with a long-term payback of 95%. It makes more sense to expose only \$1,000 to that 5% house edge, for an expected loss of \$50, than \$2,000, for an expected loss of \$100.

Play one coin at a time on Bonus Multipliers – A Bonus Multiplier is just like a Straight Multiplier, only one or more combinations pay a bonus over the straight multiple. A three-coin Double Diamond machine, which pays 800, 1,600, and 2,500 coins for the jackpot when playing one, two, or three coins, respectively, is an example of a Bonus Multiplier. The straight multiple for the three-coin jackpot is 2,400 coins, but this machine pays a 100-coin bonus for playing the third coin.

Even though Bonus Multipliers encourage you to play full coin to qualify for their juicy bonuses on some winning combinations (usually just the top jackpot), those combinations hit so infrequently that even huge bonuses on them increase the long-term payback by very little.

Let’s look at an IGT Red, White and Blue machine. One payback program available for this machine pays a 2,800-coin bonus on the top jackpot for full-coin play. The long-term payback when playing one coin at a time is 91.757%, while the long-term payback when playing three coins at a time is 92.47%. The 0.713 percentage point increase in long-term payback does not make it worthwhile to play three coins at a time, unless you also cut back on the number of spins in such a way that you give the same amount of action. If you play at the same pace, you’ll end up playing three times as much money in the machine, but you won’t get enough of an increase in payback with full-coin play to offset the increase in money you expose to the house edge.

Let’s compare the expected losses for the three styles of play: one coin at regular pace, three coins at regular pace and three coins at a slow (one-third of regular) pace. Let’s say we play through \$1,500 at regular pace playing one coin at a time. The long-term payback is 91.757% when we play one coin at a time, so the house edge is 8.243%. When we play \$1,500 against that house edge, our expected loss is 8.243% of \$1,500, or \$123.65. If we play three coins at a time at the same pace, we decrease the house edge to 7.53%, but we triple our action to \$4,500. Our expected loss is \$338.75. But if we can play three coins at a time at one-third pace, we play through only \$1,500 at the full-coin house edge and have an expected loss of only \$112.95.

It’s nearly impossible to maintain a slow pace when playing the slots. The sights and sounds of the casino are all designed to get you excited and to make you lose track of the passage of time. If you’re like me, you can keep a slow pace for a few minutes, but soon you’ll find yourself back at your regular pace and exposing too much of your bankroll. Because of the difficulty of playing at a slow pace, I recommend that players play one coin at a time on Bonus Multipliers.

I should mention one other thing about Bonus Multipliers. Many times the bonus is just a few hundred coins, but sometimes the bonus is huge, thousands of coins. If you can’t stand the thought of missing out on a big jackpot bonus because you played only one coin, do as I do and stay away from Bonus Multipliers with big bonuses.

A few years ago, I was at Bally’s Wild West casino playing one coin at a time on a bonus Multiplier that paid bonuses for full-coin play on multiple combinations. I hit one of the lower-paying bonus combinations. As I was waiting for my handpay, a passerby said that, “I bet you wish you had played full coin.”

I said, “If I had known I was going to hit on this spin, I would have played full coin.” Of course, I didn’t know that. Also, if I had been playing full coin all along, I would have run out of session money long before this spin. Instead, I chose to stretch my bankroll by playing one coin at a time and I was fairly sure that I was playing at a lower expected loss than playing full coin.

Play full coin on Buy-A-Pays – On Buy-A-Pays, additional coins buy additional winning combinations. The paytable on a Buy-A-Pay is displayed as a set of boxes, one box for each coin you can play. The box labeled “1st Coin” shows all of the winning combinations that the first coin buys and how

much each combination pays. The box labeled “2nd Coin” shows all of the winning combinations and payouts that the second coin buys, and so on. If you play only one coin and a combination bought by the second coin lands on the payline, you don’t win anything.

When you play additional coins per spin on a Buy-A-Pay, you activate additional winning combinations and you buy increased hit frequency and increased long-term payback. Sometimes the payback on the first coin played in a Buy-A-Pay is very low—sometimes even as low as the regulations in a jurisdiction allow.

One of the payback programs available for a two-coin Sizzling 7s machine pays back 95.315% when played with one coin per spin, and 98.088% when played with two coins per spin. If you played 1,000 spins, your expected loss would be 46.85 coins (4.685% of 1,000 coins) if you played one coin at a time, but only 38.24 coins (1.912% of 2,000 coins) if you played two coins at a time.

Although you’re better off playing full coin on the Sizzling 7s payback program in the machine in my example above, there are other Sizzling 7s programs in which you are better off playing only one coin at a time. I can’t guarantee that the increase in payback you buy with the additional coins will always outweigh the additional risk you have when playing more coins at a time. But because that possibility exists, I recommend playing full coin on Buy-A-Pays.

There’s another reason to play full coin on a Buy-A-Pay besides the mathematical one. It’s an emotional reason. It can be very frustrating to have a winning combination land on the payline and not get paid for it because you didn’t bet enough coins. Playing full coin eliminates that potential frustration.

Play full coin on Hybrids – Some paytables are part Buy-A-Pay, part Multiplier. One additional coin buys new winning combinations and the other multiplies the payoffs on already activated winning combinations. I call these machines Hybrids for lack of a better name.

The split personality of the Hybrid presents us with a dilemma. We know it’s not worth playing full coin on a Multiplier, but it frequently is worth playing full coin on a Buy-A-Pay. How do we reconcile this conflicting advice?

Let’s look at one of the Blazing 7s payback programs. On this machine, the second coin is a multiplier for the bar combinations and the third coin buys the payoffs on the Sevens. This payback program pays back 91.33% when played with one coin at a time, 95.10% when played with two coins at a time, and 97.18% when played with three coins at a time. Let’s play 1,000 spins on this machine. Your expected loss is 86.7 coins (8.67% of 1,000 coins) if you play one coin at a time, and 98 coins (4.90% of 2,000 coins) if you play two coins at a time. But your expected loss drops to 84.6 coins (2.82% of 3,000 coins) if you play three coins at a time. You’re better off playing full coin.

Some Hybrids have what I call a hidden Buy-A-Pay. On these machines you have to play full coin to be eligible to play a bonus game. When you have the opportunity to play a bonus game only when you play full coin, you must play full coin. There’s no way to know how much the bonus game adds to the long-term payback and the increase could be enough to make playing full coin the best bet.

You may remember a Hybrid with a hidden Buy-A-Pay slot machine from Anchor Gaming called Wheel of Gold. This machine is actually the progenitor of the Wheel of Fortune machine. You have to play three coins on a Wheel of Gold to be eligible to spin the wheel in the top box on the machine. I looked at the payback of each coin played individually, and I discovered that the amounts you could win when you spun the wheel pushed the payback of the third coin to well over 100%, 123.43% to be exact. The catch, of course, is that you have to play the first two coins, on which the house has a big edge, before you can play the third coin, on which you have the edge.

The long-term payback on this machine was 80% when you played one coin at a time and 94.99% when you played three coins at a time. Let’s say you played 1,000 spins. At one coin per pull, your expected loss is 200 coins (20% of 1,000 coins). At three coins per pull, your expected loss is only 150 coins (5% of 3,000 coins).

I always play full coin on a Hybrid and slow down my pace, but you can play less than full coin. As long as you buy all the winning combinations, you’ll be playing with the highest hit frequency possible on that machine. Your payback however may not be as high as the machine can offer. Then again, even though the additional coins may buy increased payback, the increase in payback is usually not as great as it can be on a pure Buy-a-Pay.

Play full coin on Multi-Lines – Don’t confuse this type of machine with the Multi-Line/Multi-Coin video slot. This type of machine limits you to a maximum bet of one coin per line. I don’t think you will find many of them on casino floors in the future because the video slots give players much more betting flexibility, so Multi-Line players have switched to them.

My rule on a Multi-Line paytable is to let the player choose between playing one coin and playing full coin.

Dropping one coin at a time into a Multi-Line isn’t as bad as dropping one coin at a time into a Buy-a-Pay. The additional coins played in a Multi-Line machine buy increased hit frequency and, usually, only very small increases in average payback – just like on the Bonus Multiplier. The probability of hitting the jackpot is the same on all paylines, so even a large bonus for the jackpot on the last payline leads to only a small increase in payback. The extra coins don’t have the same positive effect on expected loss that they have on the Buy-A-Pay.

Let’s look at a typical payback program for a Multi-Line machine. One of the payback programs available for a five-line Double Diamond machine pays back 88.757% when played with one coin per spin and 92.516% when played with five coins per spin. For 1,000 spins, the expected loss rises from 112.43 coins (11.243% of 1,000 coins) for one-coin play to 369.25 (7.385% of 5,000 coins) for five-coin play.

Personally, I don’t like having winning combinations land on a payline that I haven’t activated, so I always play full coin when I play Multi-Line machines, even though it’s not the right thing to do, mathematically speaking. Sometimes I put the math aside in favor of having more fun playing a machine.

Play one coin on each line on Multi-Coin/Multi-Line video slot machines – I never would have believed a few years ago that video slots would take over as much of the slot floor as they have. Some casinos today have half or more of their slot floors filled with video slots.

My rule for the number of coins to play on video slots is also to let the player choose between playing one coin at a time and one coin per line, though there’s a strong economic argument for playing only one coin at a time.

Additional coins played on a video slot usually buy only increased hit frequency, because each combination pays the same amount regardless of which payline it lands on. Playing one coin at a time stretches out your bankroll and your playing time. Playing one coin at a time, in addition, is less frustrating on a video slot than it is on a Multi-Line. The paylines on an Australian-style slot are so complicated, it’s difficult to tell when you have a winning combination land on a payline you didn’t activate.

On the other hand, most video slots are low-denomination machines, so playing one coin on each line can be a smaller wager than playing full coin on a traditional three-reel slot. In this case, you can activate each payline, get a high hit frequency, and still risk less money per spin.

Furthermore, playing more than one coin per line is rarely a good bet, since the additional coins on each line usually just multiply the amount you win for each combination on each line. With no bonus for additional coins, you’re not buying an increase in payback, so there’s no advantage to risking more of your bankroll.

Read the paytables on video slot machines very carefully. A game might require you to activate every payline to be eligible for a bonus game, so you’ll want to play all lines on those machines. Some games, in addition, advertise the huge payouts available when playing full coin on all paylines, but when you read the fine print, the payouts turn out to be straight multiples of the number of coins bet per line or the total number of coins bet, and therefore the extra coins are not worth betting.

Play full coin on all Progressives – Regardless of what type of Progressive the machine is – video, reel-spinning, standalone, wide-area — always play full coin. When you play less than full coin on a Progressive, you’re just building the jackpot for someone else, with no chance of winning it yourself.

I want to end this discussion with a word about why I make the recommendations I do and about controlling your pace when you play.

Here’s the general rule for when it makes mathematical sense to play full coin: Play “n” coins per spin if the house edge when playing “n” coins per spin is less than 1/n times the house edge when playing one coin per spin.

The house edge on the Wheel of Gold machine we looked at is 20% when you play one coin per spin and only 5.01% when you play three coins per spin.  That’s less than 1/3 times 20%.  You can play this machine with full coin at the same pace as someone playing one coin at a time and still win more in the long run.

Now let’s look at the house edge on the RWB Bonus Multiplier above. The house edge at one coin per spin is 8.243% and the house edge at three coins per spin is 7.53%, well above 2.748%, the percentage at which the expected loss for the one-coin player equals the expected loss for the full-coin player.  The machine will hammer the full-coin player if he plays at the same pace as the one-coin player.

The machine will win about three times as much money from the full-coin player, even though the full-coin player is playing at a lower house edge.  The problem is that the house edge isn’t cut low enough for the full-coin player to play at full speed.  The full-coin player gets killed because he has triple the action of the one-coin player, but his house edge isn’t lower than one-third the one-coin player’s house edge.

If the full-coin player, on the other hand, can slow down so he plays one spin for every three the one-coin player plays, he will give the same amount of action as the one-coin player, but at the full-coin’s lower house edge.  It’s true that the full-coin player will experience greater volatility because he has fewer spins (Remember the confidence intervals?), but in the long run the slow-playing full-coin player will lose less than the full-speed one-coin player.

The problem in this scenario is in playing slowly.  Controlling your pace when you play is not as easy as it sounds.  The casinos want you to play fast because they have the edge on every spin.  The more spins slot players play per hour, the more money the casinos make.

Try it some time.  Note the time that you start playing a slot.  Now play it for a few minutes and keep track of the number of spins you play.  If the slot club uses a countdown or an open formula for cashback, you can use the number of points or dollars you earned to tell you how many spins you played.  Otherwise, you’ll just have to count.  When you’re finished playing, note the length of time you played and the number of spins you played.

Now try to play one-third the number of spins in the same length of time.  Note your starting time and start playing.  When you’ve finished playing the appropriate number of spins, note the elapsed time.  It’s shorter than the elapsed time in the first trial, right?

It’s not easy to cut your pace down to one-half or one-third of your usual pace.  Because few people can effectively control their pace when they play, I recommend playing one coin at a time on some machines even though you will be playing at a higher house edge.  My goal is to limit your losses.  There are two components in your expected loss: the house edge and how much money you expose to it.  Many times, the best way to cut your expected loss is to focus on the second variable in the equation and cut the amount of money you expose to the house edge.

John Robison is the author of “The Slot Expert’s Guide
to Playing Slots.” His website is
www.slotexpert.com