Most casino players have heard that the “House always wins.” It’s not a scam or any type of conspiracy, as it all boils down to math. All casino games are designed with a built-in “advantage” that gives operators a small cut from every wager placed. This is the simplest house edge meaning and how casinos remain profitable in the long run.
The main element of risk in gambling is that you’re always fighting an uphill battle. Whether you’re betting against RNG outcomes or real dealers, that edge is working against you nearly every second.
You can “win” against the house by using disciplined budgeting strategies, prioritising titles with the house edge on casino games, and by playing in short bursts. Whether you’re wondering why do casinos have a house edge, how to reduce the house edge in blackjack, or simply want to learn the basics behind this concept, this guide covers the core principles behind the house’s mathematical advantage.
What is the House Edge, and How Does It Differ from RTP?
By simple definition, the house edge refers to the percentage of every stake that the casino keeps. This concept is directly tied to the Return to Player (RTP), which refers to the percentage of total bets that a game is expected to pay back to players over time.
The formula for calculating the house edge is equally easy – the house edge and the game’s RTP must always add up to 100%. If you know either of the two values, you can easily determine the house edge on casino games. For example, if a slot game has an RTP of 95%, the house edge is 5%. That means for every £100 wagered, the game theoretically pays back £95 to players while the casino keeps £5.
Most slot development studios simulate millions of spins on each game to determine their RTP scores. These values are transparently listed on the websites of game makers, but plenty of UK-licensed casinos have dedicated pages where you can learn the exact RTPs of every offered slot, table game, or live dealer title.
How Is the House Edge Built Into Different Casino Games?
Each type of casino game operates with a mechanism that creates the house edge. Below are some of the most notable examples:
Roulette – Zero and Double Zero Pockets
All European roulette wheels come with 37 pockets, including 36 numbered positions and a single zero. American roulette games have an extra zero, but cover the same numbers as European roulette versions. The house edge in both versions comes from the fact that the payout odds don’t reflect the “true probability” of winning.
For example, a straight-up bet (single wager on a number) has a payout rate of 35:1, but the true odds are 1 in 37 since there are 37 betting fields (36 numbers + zero). In theory, covering the entire board would result in a single win that covers all other losing bets. In practice, the casino gives you a lower payout rate to turn a profit – 1 in 37 gives you a 2.70% odds of winning a bet that pays 35 to 1. This means that the casino’s edge in this case is 2.70%, while the RTP is 97.30%.
The same logic applies in American roulette, but the added zero worsens the odds. A straight-up bet still pays 35:1, but the true odds are 1 in 38, leading to a higher house edge of 5.26%. This is why most UK players (and UK-licensed casinos) stick to European roulette.
Blackjack – Dealer’s Initiative Creates an Advantage
The basic rules of blackjack state that whoever reaches 21 without going bust wins the round. The house edge in blackjack comes from the fact that the player acts before the (casino’s) dealer. You can go over 21 before the dealer even gets the chance to play, which results in an instant loss.
Let’s assume that both you and the dealer will always stick to the same strategy for 20 hands. You’ll eventually be forced to hit when drawing risky hands (e.g., 12 to 16), and you’ll lose some rounds. With the same cards, the dealer would’ve lost, too, but they’re playing after you. This is how casinos secure an edge in blackjack.
In most cases, blackjack games have an ultra-low house edge of just 0.5% to 2%. Your strategy and in-game choices may greatly affect the game’s RTP, though.
Baccarat – Commissions on Banker Hand Bets
Baccarat may appear as a passive game where you simply bet on outcomes without directly being involved with the cards, but several nuanced rules keep things interesting – and create an advantage for the casino.
The house edge comes from the Banker hand, which statistically wins more often than the Player hand. That’s because the Banker acts after the Player and follows rigid drawing rules that slightly improve their odds, similar to how dealers benefit in blackjack.
To account for this advantage, a 5% commission is typically applied to all winning Banker bets. Without this deduction, the Banker side would be the clearly optimal choice every round.
While you can also bet on Ties, Pairs, or other side bets, these usually carry much higher house edges. Standard Baccarat has a house edge of:
- 1.06% on Banker Hands
- 1.24% on Player Hands
- 14.36% on Tie Bets
Some No Commission Baccarat variants eliminate the 5% fee, but adjust payouts to preserve the edge by, for example, only paying 1:2 when the Banker wins with a 6 instead of paying 1:1.
Slots – Software-based Advantage
Unlike table games, slots don’t involve visible rules like zero pockets or card drawing orders. Instead, the house edge is hidden in the math behind reel symbols, payout odds, and hit frequencies.
Every spin’s outcome is determined by Random Number Generator (RNG) software, which is calibrated to return a specific percentage of all bets back to players over time. That percentage is known as RTP (Return to Player), and the difference between 100% and the RTP is the house edge.
The example below is how house edge vs RTP can be explained best:
Let’s say that a slot has a maximum win limit of 1,000x, which can be unlocked by landing 5 scatters. To expand on this example, let’s assume that you’re betting £1 per spin and that the hit frequency for the maximum win is 1 in 100,000. In this case, the true value of the top win would be £1,000 times (1/100,000), which equals £0.01 value per round.
Even in basic slots, there are dozens, if not hundreds or thousands, of unique symbol combinations with unique disparities between true odds and fixed payouts. Here, the house edge comes from the fact that the average payouts are lower than the wagered amount. By design, you’re expected to lose more than you’ve staked in the long run.
How Do You Calculate the House Edge? (The Formula Explained)
Now that we’ve covered what does house edge mean, let’s talk about the math behind the works.
The house edge formula is universal and always calculated by dividing the expected value of loss by your initial wager, which is then multiplied by 100. In case you’re unfamiliar with these terms, let’s explain each variable:
- Expected Loss: This represents the amount of money you’re statistically likely to lose over long periods
- Initial Wager: Sometimes called the Betting Unit, this is the size of the bet you’re using each round
- Why Multiply by 100? The house edge is always expressed as a percentage, which is why we multiply by 100. Remember, house edge plus RTP must always equal 100%. Unlike unpredictable live gaming odds, casino slot games are based on fixed outcomes and programmed probability curves. There are no unknowns, and anything over or under 100% would break that closed system.
Example of Calculating the House Edge with a Coin Flip
A Coin Flip is one of the best games we can use to illustrate how house edge calculations work because there are only two outcomes and no ties – the Coin may either land on its head or tail.
For this example, we’ll use a biased coin flip, where Heads land 45%, and Tails land 55% of the time. Additionally, we’ll set £1 as the standard betting unit, and every outcome pays out 1:1. In other words, successfully calling Heads would give you £2, while missing the prediction is a loss.
To calculate the house edge based on this example, just follow the steps below:
- Step 1: Calculate expected returns
Turn the percentages from each outcome into decimal values and multiply them by the amount of money you can win to determine the total expected return. If you were only betting on Heads, you’d stand to gain 0.45 x £2, meaning £0.90 per round. - Step 2: Determine the expected loss
For the next step, deduct your expected returns from your initial wager. You’re getting £0.90 for every pound you wager, meaning that your expected loss is £1 – £0.90 = £0.10 per round. - Step 3: Use the house edge formula
Now that you have both variables, it’s time to divide your expected losses by your initial wager and multiply the outcome by 100 to reform the result into a percentage-based value. In this case, you’re dividing £0.10 by £1; when multiplied by 100, we’ll get 0.10, or 10%.
Which Casino Games Have the Lowest House Edge?
Choosing casino games with a low house edge is one of the simplest ways to get more value from your bets. They don’t guarantee consistent returns, but they’re statistically more likely to give you a fair chance of winning than slots with subpar RTP scores.
Below is a list of the lowest house edge casino games UK, as well as the conditions that must be met to bring the casino’s advantage to a minimum:
| Casino Game | Lowest House Edge (%) | Specific Bet/Condition | Notes |
|---|---|---|---|
| Blackjack | 0.5% | Dealer Stands Soft 17 | Reduce the house edge by 0.22% by exploiting the mandatory “stand” on Dealer’s 17 |
| French Roulette | 1.25% | La Partage and En Prison rules | Unique rules in French roulette that give your bets a second chance when zero hits |
| Baccarat | 1.06% | No Commission | No commissions are paid on Banker bets, which are statistically more likely to win than Player hands |
| Craps | 0.5-1.5% | Pass/Don’t Pass and Come/Don’t Come, followed by Odds bets | Use standard Pass/Come bets until a point is established, and follow up with Odds bets to capitalise on the lowest house edge in craps |
| Video Poker | 1-5% | Jacks or Better variant | Specific video poker games have inherently lower house edge values; no particular bets can reduce it |
| Slots | 2-15% | Prioritise high-RTP games from renowned studios | Games like Relax Gaming’s Epic Joker have some of the lowest house edge scores in the industry |
What is the “Element of Risk,” and Why Is It a Better Metric?
House edge and Return to Player are the two most common metrics used by most players to determine the long-term (theoretical) profitability of specific games. There’s another metric that’s mainly used by more experienced players, called the Element of Risk. It’s not a universal metric like house edge and RTP since it exclusively applies to games where you can make additional betting options on top of your initial wager mid-round.
The EOR reflects how much you’re risking on average, including every penny or pound you’ve staked on side bets, such as double downs in blackjack or raises in poker. While not traditionally measured using EOR, features like Bonus Buy or Ante Bet mechanics in slots do alter your effective wager. In theory, you could assess risk using similar logic, though it’s not standardised in slot design.
The Element of Risk can be explained as a modified house edge, adjusted by your total wagered amount per round in place of the initial wager. Let’s illustrate how it works with an example.
Let’s say you’re betting £1 per standard round on Blackjack. If you use double-down once every 5 games, you’ll effectively bet £120 (£100 on standard bets + £20 on double-downs).
In this case, the house edge may be just 1% based on your original bets, but you’re putting £1.20 on the line on average. The element of risk formula divides the standard house edge by your average wagered amount; in this case, it’s 1% / 1.20 = 0.83%. With this adjusted house edge, the casino actually keeps 0.83% of the bets you placed instead of 1%.
Why Are Side Bets a Trap? (House Edge vs. Volatility)
Gambling often boils down to simple binary logic – a bet can either win or lose. The best way to explain why side bets are a trap is that you’re adding another variable – your starting bet can win or lose, but if it wins, you win again with your side bet to keep your earnings.
Let’s explain this with Blackjack as an example. Suppose you’re normally wagering £1 per hand. You should be making relatively consistent winnings if you stick with a standard strategy since the house edge is only 0.5%. However, if you were to use the Perfect Pairs side bet, the house edge would skyrocket to 6-11%, depending on whether you opted for a Perfect, Coloured, or Mixed Pair.
The payout rates for these extra options are more generous; Mixed pairs pay 5 to 1, Coloured pairs pay 10 to 1, while Perfect Pairs pay 30 to 1. However, let’s see the conditions that have to be met for your side bet to qualify:
- A mixed pair is achieved by drawing two cards with the same numerical value, but different suits and colour.
- A coloured pair has the same color, but different suits.
- A perfect pair is comprised of identical cards – same colour, same suit.
Consider this – your side bet must meet the abovementioned criteria, or you instantly lose, regardless of how great your hand was. If we take Evolution’s Blackjack, which traditionally uses 8 decks, the probability of winning these side bets is as follows:
- Mixed pairs: 16 in 415, meaning 3.86%, the payout ratio is 5:1.
- Coloured pairs: 8 in 415, meaning 1.93%, the payout ratio is 10 to 1.
- Perfect pair: 7 in 415, meaning 1.69%, the payout ratio is 30 to 1.
There are plenty of other gaming types where you can place side bets, at the expense of playing with a much greater handicap.
In Baccarat, options like Player Pair, Banker Pair, and Perfect Pair can pay out 11:1 or more, but their house edges often range from 10% to over 15%, depending on the variant. While the main Banker/Player bets have under 1.5% edge, these side bets can be five to ten times worse in terms of expected return.
In European and French roulette, the house edge is relatively low (around 2.7%), but many variants offer “racetrack” bets like Orphelins, Tiers du Cylindre, or Zero Game, which include complex combinations with lower hit frequencies and no improvement in RTP. Even some “fast roulette” games can trick players into playing more often without increasing expected return.
How Does the UKGC Ensure Fairness in House Edge?
The United Kingdom Gambling Commission (UKGC) is the official regulatory body responsible for overseeing all forms of legal gambling in the UK. It has the authority to suspend licenses, issue fines, or shut down operators that fail to meet its strict standards for fairness and transparency.
According to UKGC requirements, all RNG-based games (slots, table games, video poker, etc.) must be tested by independent, UKGC-approved organisations, such as eCOGRA, iTech Labs, or Gaming Laboratories International (GLI). These tests confirm that each game operates with genuine randomness and that long-term return figures align with the stated values.
Furthermore, UKGC-licensed casinos are obligated to clearly display the RTP or house edge for every game they offer. Most games include this information in their paytables.
Conclusion: Playing with Mathematical Knowledge
Knowing what is house edge in casinos is half the battle; the other half revolves around forming a strong strategy suited for your bankroll and the chosen game type. Remember that a low casino house edge doesn’t guarantee you’ll win; it’s a theoretical construct that explains how much of a handicap you’re playing with.
The best way to get a feel for how house edge and RTPs work in real life is to play demos. Whether you’re into slots, RNG table games, or live dealers, most games can be practised before putting real money on the line, and firsthand experience is the best (and fastest) teacher.