Online casino games are built with a mathematical advantage for the operator, known as the house edge. Understanding it helps set clear expectations before deciding whether to play.
Terms like house edge and RTP appear in game info screens all the time, yet it is not always obvious how they’re worked out or why they matter. Once you grasp them, you can compare games more confidently.
This guide explains what house edge means, how it relates to RTP, how it’s calculated, how rules affect it across popular games, and how regulation keeps things in check. It also clears up common myths and shows how to use the house edge when deciding what to play.
Read on to learn more.
What Is The House Edge In Online Casinos?
The house edge is the average percentage of each bet a casino expects to retain over the long run. It reflects how much the rules and payouts of a game tilt outcomes in the casino’s favour.
If a game has a 5% house edge, that means that, across a large volume of bets, about £5 of every £100 wagered would, on average, remain with the casino. The rest is returned to players as winnings. This percentage is built into every game by design, so it varies between slots, roulette, blackjack and everything else.
Put another way, house edge gives a long-term picture. What happens in a short session will swing around that number. With that in mind, how does it compare to RTP?
How Does House Edge Differ From RTP?
The house edge and RTP describe two sides of the same coin. The house edge is the casino’s long-term share of total wagers. RTP, or Return to Player, is the share returned to players as winnings over time.
They add up to 100%. A game with a 96% RTP has a 4% house edge. The 96% figure is theoretical and based on a very large number of plays. Over a short session, actual results can be very different, which is why RTP is best used for comparison rather than prediction.
With the relationship clear, the next step is seeing how the house edge number is worked out.
How Is House Edge Calculated For Simple Bets?
For straightforward bets, the house edge comes from the gap between true odds and the payout offered.
Take a coin toss. The true chance of heads is 50%. If a casino offered a payout of less than 1:1 on correctly calling heads, the difference between the fair return and the actual payout would create a house edge.
A casino example makes this clearer. On European roulette, an even-money bet such as red/black wins if any of 18 numbers land out of 37 possible outcomes. The true probability is 18/37, but the payout is 1:1. Over time, the average return works out at 36 paid units for every 37 wagered, which means a house edge of 1/37, or about 2.70%.
The same principle applies across games: compare the true probabilities with the payouts, then express the shortfall as a percentage of the original stake.
House Edge On Popular Online Casino Games
Different games have different built-in advantages. Knowing the typical ranges helps when comparing options.
Slots
Slots usually express their advantage through RTP. Many online slots sit around 95% to 97% RTP, which equates to a house edge of roughly 3% to 5%, though some titles fall outside this band. Some games are released in multiple RTP versions; the version shown in the game’s help or info screen is the one that applies on that site.
Roulette
The wheel layout and rules make a noticeable difference. European roulette, with a single zero, has a house edge of about 2.70% on most bets. American roulette adds a double zero, pushing the edge to around 5.26%. Some French roulette tables use rules such as la partage or en prison on even-money bets, which can reduce the effective edge to about 1.35% for those specific wagers.
Blackjack
Blackjack can offer one of the lowest house edges when using basic strategy, sometimes under 1%. Small rule changes matter. For example, paying 3:2 on a natural blackjack keeps the edge lower than 6:5 payouts. Whether the dealer stands or hits on soft 17, doubling options, and the number of decks all move the figure up or down.
Baccarat
Baccarat is simple but not uniform across bets. Banker bets typically carry a house edge of around 1.06%, player bets about 1.24%. Tie bets are much higher because the payout rarely matches the true odds; the exact edge depends on whether the tie pays 8:1 or 9:1.
These benchmark figures help for comparison, but they are averages. Short-term outcomes can land above or below them.
How Does House Edge Affect Your Expected Return?
The house edge is a guide to your long-run return per pound staked. With a 4% house edge, the long-term average return is about 96p for every £1 wagered. That does not tell you what will happen in any single sitting, but it does set expectations over time.
It also helps to separate return from pace. House edge estimates the proportion of stakes retained on average, while stake size and spins or hands per hour determine how quickly that cost plays out during a session.
Can The House Edge Change With Game Rules Or Stake Size?
Rules can shift the house edge noticeably. In blackjack, changing from a 3:2 to a 6:5 payout on a natural blackjack increases the edge. Allowing or restricting doubling or splitting, or altering whether the dealer stands on soft 17, also moves the number. In roulette, switching between European and American wheels has a clear effect. Side bets in card games often carry their own, usually higher, edges.
Stake size does not change the house edge. Betting more or less affects how much you might win or lose in cash terms, but the underlying percentage advantage stays the same. Promotions, features or progressive jackpots can alter returns on specific wagers, so the paytable and rules are the best places to check details.
How Do Regulators And Operators Ensure House Edge Is Fair?
Regulators such as the UK Gambling Commission set standards so that games are presented and operated as advertised. Before release, games are tested by independent laboratories to verify that the maths, including RTP, matches the design.
Random number generators are examined to ensure outcomes are unpredictable and not manipulated. Licensed operators must display accurate game information, including RTP or house edge where applicable, and keep it up to date. Periodic audits check that live games continue to perform within their certified parameters, and non-compliance can trigger enforcement action.
This framework is designed to give players confidence that published figures reflect how the games actually operate.
Common Misconceptions About House Edge
The house edge predicts what will happen in a single session. It does not. It describes long-run averages across a very large number of bets.
A lower house edge guarantees better results for every player. It increases the expected return over time, but individual results still vary.
Betting systems can remove the house edge. Altering stake patterns cannot change the underlying expected value of a bet. In strategy games like blackjack, optimal play can reduce the edge, but it does not erase it.
Past outcomes influence the next spin or deal. Each spin of a properly tested roulette wheel or slot is an independent event, so previous results do not make a particular outcome “due.”
All games have similar edges. They do not. Edges differ between game types and even between versions of the same game.
How To Use House Edge When Choosing Games?
The house edge is a practical comparison tool. If two games appeal equally, choosing the one with a lower house edge means, on average, more of your stake is paid back over time. Checking the game info or help section for RTP or the house edge, and scanning the rules for variations that affect it, is a sensible starting point. On our site, we show the figures provided by operators so you can compare them before you play.
Personal preference still matters. Some players value simple rules and steady pacing; others prefer features or formats that offer bigger swings. The house edge does not forecast what will happen tonight, but it does help set expectations and choose games that fit how you like to play.
If you choose to play, set personal limits that suit your circumstances, take regular breaks, and only stake what you can afford to lose. If gambling starts to affect your well-being or finances, seek support early.
**The information provided in this blog is intended for educational purposes and should not be construed as betting advice or a guarantee of success. Always gamble responsibly.