How Casino Bonuses Affect Game Odds: Factoring Casino Bonuses Into Your Budget and a Game’s RTP

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Online casino bonuses can seem quite generous at times, but it’s rare to find ones that don’t come with strings attached. From the casino’s point of view, the bonus is an enticement for you to play more. If you don’t, it isn’t worth it for them.

Often, that means the bonus requires a certain amount of play to clear or to unlock. Other times, it might appear to be a free gift, but comes after you’ve already lost a bit of money to the casino. In those cases, they’re giving you a little back to get you to stick around.

That means it might be better to think of these bonuses in terms of offsetting your losses, or reducing the house edge, rather than as “free money.”

If a shoe store offers you $10 off on a purchase of $100 or more, you understand that you’re not really getting $10—you’re just spending less for the same thing. It feels different with a casino because there’s always the chance of walking away with more than you started with. However, if you think in terms of expected winnings and losses, it works out to be pretty much the same thing.

In our other Casino School probability lessons, we’ve shown you how to work out your expected losses and budget for them. Here, we’re looking at factoring bonuses into that. There are two different ways of looking at this:

  • Offsetting Bonuses Against Expected Losses
  • Adjusting the RTP for Bonuses

Then, we’ll see how possible it is to turn a profit at a casino using bonuses.

Online casino bonuses can seem quite generous at times, but it’s rare to find ones that don’t come with strings attached. From the casino’s point of view, the bonus is an enticement for you to play more. If you don’t, it isn’t worth it for them.

Often, that means the bonus requires a certain amount of play to clear or to unlock. Other times, it might appear to be a free gift, but comes after you’ve already lost a bit of money to the casino. In those cases, they’re giving you a little back to get you to stick around.

That means it might be better to think of these bonuses in terms of offsetting your losses, or reducing the house edge, rather than as “free money.”

If a shoe store offers you $10 off on a purchase of $100 or more, you understand that you’re not really getting $10—you’re just spending less for the same thing. It feels different with a casino because there’s always the chance of walking away with more than you started with. However, if you think in terms of expected winnings and losses, it works out to be pretty much the same thing.

In our other Casino School probability lessons, we’ve shown you how to work out your expected losses and budget for them. Here, we’re looking at factoring bonuses into that. There are two different ways of looking at this:

  • Offsetting Bonuses Against Expected Losses
  • Adjusting the RTP for Bonuses

Then, we’ll see how possible it is to turn a profit at a casino using bonuses.

Offsetting Bonuses Against Expected Losses

The simplest way of looking at things is to figure out how much you’re losing on average, and subtract that from the bonus or vice versa.

  • Calculate your bonus value in dollars.
  • Calculate your expected gross losses in dollars.
  • Subtract the smaller number from the bigger one.
  • If the bonus was bigger, you’re looking at an expected net win. If the gross losses were bigger, you’re looking at an expected net loss.

One of the common conditions you’ll see attached to a bonus is a playthrough requirement. In a nutshell, that means you need to bet a certain amount—typically a multiple of the bonus amount—to get your bonus.

Let’s say you have a $100 bonus with a 30x playthrough requirement and you’re going to play slots to clear it. That means you’ll need to bet $3000 on slots.

A typical return-to-player (RTP) for online slots is 96%. Flipping that around, this means there’s a 4% house edge. 

Your expected losses from playing $3000 worth of spins on a 96% RTP slot are 4% of $3000, or $120.

But after playing that much, you get your $100 guaranteed bonus. So you can subtract that from your expected losses. After collecting a $100 bonus, you expect that, on average, you’ll only be down $20, not $120.

That bonus doesn’t work out to be “free money” because you’ll still lose more than you win on average. But it does mean you’re gambling at a discount.

Adjusting the RTP for Bonuses

The other way of looking at things is to factor in the bonus up front and adjust the game’s effective RTP to account for it.

  • Calculate your bonus value in dollars.
  • Divide that by the amount you have to stake to claim the bonus to get the net impact on RTP.
  • Add that to the game’s baseline RTP.

For some types of bonuses, this might mean digging into the Terms & Conditions and pulling out a calculator.

Let’s say the casino offers you a free spins on a particular slot for every $100 you play at roulette. You look at the T&Cs and see that you’ll get five free spins 90% of the time, and 25 free spins 10% of the time. 

So, that’s an average of (90% x 5) + (10% x 25) = 7 free spins. These are $0.40 denomination spins and the slot has an RTP of 96%, so they’re each statistically worth $0.384. Multiplied by 7 means that, all told, the bonus is worth an average of $2.688.

You have to stake $100 at roulette to get that. So, that bonus represents an adjustment of 2.688% to your RTP—$2.688 divided by $100.

If the casino is offering you single-zero European roulette, the base RTP for that is 97.2973%

Adding the 2.688% gets you 99.9853%, very close to 100%.

In other words, if you’re taking full advantage of that bonus, you’re going to break just about even on average.

Can You Turn a Profit at a Casino Using Bonuses?

In the examples above, the bonus amounts are slightly smaller than the statistical cost of unlocking them. Getting the bonus makes you much more likely to break even, but you’d still be losing a little money on average.

That isn’t always the case. More favorable casino bonuses do sometimes allow you to enjoy an edge over the house. For instance, if the first bonus only had a 20x playthrough requirement, you’d be making $20 on average by clearing your bonus, rather than losing $20. In the second example, if the bonus were any more generous with free spins, the effective RTP for playing roulette would be over 100%.

Before you get too excited about beating the house, however, there a few things to note.

First, gambling with the expectation of turning a profit is a risk factor for developing a problem. That’s true even when the expectation is statistically justifiable. Bonus recommends only gambling for fun, and with money you can afford to lose.

Second, the variance you’ll experience is certainly going to be much, much larger than any statistical profitability. Going back to the first example, it’s very easy to be down (or up) several hundred dollars after playing $2000 or $3000 worth of spins on a slot machine. So, whether your bonus is statistically worth plus $20 or minus $20 after you clear it, that’s going to be dwarfed by whether you got lucky or not. In other words, you’re still gambling no matter what.

Finally, casinos don’t want players who are only interested in exploiting bonuses to gain an edge. If you limit your play to spots where your RTP is over 100%, you will pretty quickly find that you don’t get offered any more bonuses.

Are Casino Bonuses Worth It?

Keep in mind that the best casino strategy is the one that gets you the best entertainment value for your money.

Even ignoring all the risks, let’s say you spend four hours clearing your bonus. The question isn’t whether you were going to profit $20 or lose $20 on average. Because even if you’re profiting, it’s going to work out to $5 per hour. You’re better off doing almost anything else if making money is the goal.

The question is: Did you enjoy playing slots for four hours?

If you did, then getting to do so at a $100 discount is definitely worthwhile. If not, then the better decision is not to play, regardless of what bonus is on offer.

So why calculate the impact of bonuses at all? Because of the times that they’ll affect your game selection or stakes.

Going back to the shoe sale analogy, maybe you went into the store intending to buy a pair of brown shoes but found similar black ones for $10 off. Is that enough to change your decision? That depends on how strong your color preference is.

The same logic applies to casino promotions pushing you toward a game you don’t normally play. Maybe you wanted to play slots but that roulette promotion looks interesting. Being able to tell how generous or how stingy that promotion is will help you make an informed decision on how you spend your entertainment budget.

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About the Author

Alex Weldon

Alex Weldon

Alex Weldon is an online gambling industry analyst with nearly ten years of experience. He currently serves as Casino News Managing Editor for Bonus.com, part of the Catena Media Network. Other gambling news sites he has contributed to include PlayUSA and Online Poker Report, and his writing has been cited in The Atlantic.
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