House Edge In Online Casino Slots

House Edge in Online Casino Slots: What You Need to Know

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Updated on: 10 Apr 2024
Dean McHugh

Online slots are great fun to play, but let’s be honest: it’s not just about enjoying yourself; everyone wants to win some money too. While nothing is ever guaranteed, playing online casino slots offers the potential to collect real cash prizes - but to do this, you’ll have to face the house edge.

Every casino has a house edge over the player, but it doesn’t always unfold in the same way. How can you beat the house edge? And how can you find online slots with the lowest house edge? We’ll cover these questions and more in our easy-to-follow house edge guide.

What is a House Edge and How Does It Work With Slots?

Another way to describe house edge would be the house advantage, and it’s the method that casinos use to ensure that they collect more money than they pay out.

While it’s perfectly possible to walk away with a profit after a session playing online slots, the casino has a better chance statistically. This is what’s known as the house edge.

The house edge is usually expressed as a percentage, and can vary from 1% to 10%, or more. The lower the house edge percentage, the better this is for the player as this percentage figure represents the size of the advantage that the casino holds.

With some types of casino games, the house edge is always the same, unless there’s a version released that has a variation in the rules. For example, the house edge for standard European roulette is 2.76%.

For slots, the house edge is different for every game, so it’s important to check before you start playing. For example, the house edge for Starburst is 3.9%, while the house edge for Gonzo’s Quest is 4%. What’s particularly interesting about this is that both slots are made by industry giant NetEnt, demonstrating that even slots from the same software provider can be very different. You can find slots with an even lower house edge; Blood Suckers - also by NetEnt - has a house edge of just 2%.

Although every slot can have a different house edge, the principle still works in the same way. The mathematical mechanics of the game have been set up to give the casino a greater probability of winning when it’s played over an extended period of time.

What’s important to understand about the house edge is that it reflects the statistical likelihood. This doesn’t mean this will be the same when you play. A house edge is based on the probable outcomes when played for a very long period, far greater than any single session. Therefore, when you play slots, the outcome may be different. The casino may collect more than their house edge if you have a losing session, or if you hit a hot streak, you might end up with more than you started with.

Understanding RTP

The house edge for many casino games is often used as a measure for players. It’s a useful tool in determining the probability of winning a game.

However, the house edge is rarely quoted for slots; instead, a measure called RTP is typically used.

RTP is an acronym for “Return To Player”, and it measures the same thing as a house edge, but in the opposite way. While a house edge measures the advantage a casino holds, the RTP describes the probability of a player winning.

In the previous section, we described Gonzo’s Quest as having a house edge of 4%. This slot is more commonly described as having an RTP of 96%. When you put these two figures together, you can see how they are two sides of the same coin. To give a second example, the RTP of Starburst is 96.1%, which again, together with the house edge of 3.9%, provides the full picture.

You can use either the house edge or RTP to understand the probability of winning a game; they both describe the same thing. The RTP is typically used to express this figure for slots, but it’s easy to work out the house edge once you know the RTP if this is your preference.

Just like the house edge, the RTP is simply an indication of the probable outcome when the game is played for a very long time. It provides a statistical insight, but your playing experience could be significantly better or worse depending on your luck and your strategy (but more about that below).

It’s also worth emphasising here that while a low house edge is preferable for players, the opposite is true for the RTP. The higher the RTP, the better your statistical chances of winning from the slot.

House Edge And The Impact of Volatility

Casino slot and volatility

It’s important to check a slot's RTP, as it provides valuable insight into the probable outcome. While a high RTP doesn’t guarantee a payout, it does mean there’s a better chance the game will pay out.

However, another statistic that can affect the playing experience and the winnings you might collect is volatility, which is typically described as low, medium, or high.

A slot with low volatility means that winnings will appear regularly but will typically be for a smaller amount. This doesn’t mean that you’ll never win larger prizes, but that these will be rarer. At the opposite end of the scale are high volatility slots. These pay out much less frequently, but with the typical win having a higher value. A high volatility slot doesn’t mean you’ll be regularly collecting jackpot wins, but there will be fewer low-value spins.

A medium volatility slot sits in the middle of these two extremes, with reasonably regular wins of an average amount.

The precise value of the payouts depends on the range of the slot you are playing, and the stake you have wagered.

The volatility of a game will have an impact on how you play. If a casino slot has a high RTP but also a high volatility, you might have long periods without a win. This doesn’t mean that the RTP is inaccurate, but the larger, less frequent payouts are what pushes the RTP figure up. If you don’t have a generous budget and a sensible strategy, high volatility slots can be hard to manage.

Conversely, a slot with a low RTP might deliver very frequent wins if it has low volatility. The low value of these wins means that the RTP is still an accurate reflection of the statistical likelihood, but just paid out in a different way.

So what does all of this mean for the house edge? Let’s be clear: volatility doesn’t change the advertised house edge or RTP. However, the playing experience can be altered by the volatility. If you are playing a slot with high volatility, the house edge may feel much higher if you are on a long stretch without any wins. This is why the two factors should always be considered together. Volatility describes the frequency of the theoretical hit rate, but considered on its own, it’s not that helpful. The house edge/RTP is the critical part, as this describes how high the potential returns could be.

Regulatory Bodies and Their Role

It’s never advisable to play at an unlicensed casino. This is true for several reasons, such as the security of your personal data. However, one of the other reasons is that regulatory bodies set out high standards for the conduct of casinos, including the fairness of their games.

All casinos must be fair and transparent when offering online slots. Information in regards to RTP must be easily available to the player. The regulators do not stipulate the maximum house edge that a casino can impose. But, there is a minimum RTP which is usually around 85% depending on the governing regulator. The most important thing is, that the player must be able to see the statistical likelihood of winning each game, enabling them to make an informed decision. This means that the casino must make the house edge and/or RTP clear on their site.

In addition, regulatory bodies such as the UK Gambling Commission expect the advertised house edge and/or RTP to be accurate, and for it to have been tested using independent, certified bodies. Casinos are not permitted to manipulate the house edge in their favour.

This doesn’t mean that this is the house edge that you’ll experience when playing the game, but it ensures that you can make a fair comparison between different slots.

Common Misconceptions About the House Edge

A closer look at house edge

The house edge is the enemy of the player; the higher the house edge, the lower your statistical chance of winning. The great thing about playing slots is that it’s possible to seek out games with the best RTP.

However, before you dive in to find the best slots to play, there are a few misconceptions about house edge and RTP to address.

1. The House Edge Means You Can Never Win

It’s true that the casino will always have the statistical advantage, but this doesn’t mean that it always wins. Remember, the house edge or RTP has been calculated based on millions of spins and represents an overall average.

A higher RTP and lower house edge means the casino has less of an advantage, but you can theoretically win with any slot, even those with a lower RTP. The outcome of every spin is random; this is a requirement set out by the regulator. Therefore, even though the house edge is real, due to the number of games played in a session, the actual experience can be very different.

2. The Casino Can Manipulate the RTP

As mentioned above, regulators are very interested in the honesty and integrity of licensed casinos. When you play at a licensed casino, the games will be fair and transparent.

The regulators stipulate that slots must use a Random Number Generator (RNG), and that this is certified by an approved, independent body. Casinos will be monitored to ensure that there is no interference in how the RNG works.

All of this means that you can trust that the RTP is an accurate reflection of the statistical likelihood of winning. Casinos are not allowed to manipulate the games or the RTP to give players fewer wins.

However, this doesn’t mean that you’ll have the same experience at every online casino. For some slots, there is a range for the RTP rather than a single fixed figure. This means by comparing the RTP at different casinos, it’s sometimes possible to get better odds.

For example, Book of Dead has an RTP range of 84.18% to 96.21%, with a default RTP of 96.21% set by the software provider Play’n GO. Starburst is another good example of a variable RTP; many casinos offer the standard RTP of 96.10% but it can drop as low as 93.05%. Differences in the RTP can significantly alter your playing experience so it’s always worth checking at the start.

3. If a Slot Hasn’t Paid Out For a While, It’s Due a Win

We’ve said it a few times already, but it’s worth emphasising: the RTP and house edge is just a statistical calculation based on probability. Your playing experience might be very different, and there’s no guarantee of a win or a loss on any spin.

As slots use an RNG to determine the outcome, you have the same statistical chance on every spin. Not winning on the previous spin doesn’t increase your chances of winning on the next spin. The RNG isn’t influenced by the memory of previous spins; the slate is effectively wiped clean on every turn. Therefore, if a slot hasn’t paid out for a while, it’s no indication that it’s “due” for a win. Use the RTP and volatility to determine the statistical probability of a win, not when the slot last paid out.

4. Low RTP Slots Never Pay Out Big Prizes

Although it’s usually a good idea to aim for slots with a high RTP, there is a theoretical chance of winning on any game. Mega Moolah has a low volatility, and when jackpot wins are excluded from the calculation, the RTP is as low as 88.12%.

However, Mega Moolah has a progressive jackpot and has created tens of millionaires in the past two decades. It’s possible to win a jackpot from any type of slot where it’s on offer, regardless of the RTP and house edge.

Top Tips for Maximising Your Wins

Let’s be clear here: slots are a game of chance, and there’s no way you can influence what lands on the reels. You pay your stake, spin the reels, and there’s nothing you can do to change the result.

Anyone who offers you guaranteed wins playing slots isn’t being completely transparent with you. However, that doesn’t mean you can’t adopt a strategy that gives you the best possible chance of winning and maximising your returns.

Confused? It’s all about strategy and smart bankroll management.

As we described above, some games have high volatility, and some have low volatility. The strategy you adopt should take into account the volatility of the game, as well as the RTP.

In a slot that has higher volatility, you’ll need to be able to endure longer spells without a win. If you play with a high stake, you could burn through your bankroll quickly, leaving you unable to keep playing to collect the payout. With high-volatility slots, it’s all about surviving until the next large payout in the hope that one of them will offer a really big win. Tight bankroll management is absolutely vital.

With low-volatility slots, you should have plenty of small wins along the way. This helps to keep your bankroll topped up, and lessens your chance of blowing your whole budget within a few spins. Of course, it’s much harder to land the larger wins, so you’ll still need to calculate the right amount to wager. But with small wins hitting frequently, it’s not such a challenge to stay in the game.

There are strategies that can be used when gambling, such as Martingale. However, these typically deliver better outcomes in casino games with a 50/50 chance of winning, so they’re not particularly useful for slots. Having a strict budget for play and calculating how much you can afford to spend on every spin is a far more effective way of maximising your potential returns.


Although winning on slots relies on good fortune, there are ways to maximise your chances of a positive outcome, and that’s by choosing a game with a low house edge. Look for slots with a high RTP and match the volatility to your playing style, and you’ll give yourself the very best chance of a win - and who knows, you might even beat the casino.

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