House edge explained: what it is, why it matters, and how much it costs you
Every casino game, slot machine, and betting market has a built-in mathematical advantage for the operator. It's called the house edge, and it's the reason casinos always win in the long run — even though individual players can and do win every day. This guide explains what the house edge is, how it works across different games, and what it actually costs you in real money.
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What is the house edge?
The house edge is the percentage of each bet that the casino or bookmaker expects to keep over time. It's a mathematical average, not a prediction for any single bet.
At European roulette, the house edge is 2.70%. This means that for every £100 wagered across all players over time, the casino keeps £2.70 and returns £97.30 as winnings. You might win £500 in a single session or lose £200 — but across millions of spins, the casino's take converges on 2.70%.
The house edge exists because the odds offered are slightly less generous than the true probability of winning. In roulette, there are 37 numbers (1–36 plus 0), but a winning bet on a single number pays 35 to 1 — not 36 to 1. That gap between the true odds and the payout is the house edge.
Every form of gambling has one. It's not a secret and it's not a conspiracy — it's the business model. Understanding it is the single most important thing a gambler can learn.
What is RTP — and how does it relate to the house edge?
RTP stands for Return to Player. It's simply the other side of the house edge.
House edge + RTP = 100%
If the house edge is 2.70%, the RTP is 97.30%. If a slot machine has an RTP of 96%, the house edge is 4%.
RTP is the term you'll see most often with online slots and casino games, because regulators require operators to publish it. When a slot is advertised as "96% RTP," it means that over millions of spins, 96p of every £1 wagered is returned as prizes and 4p is kept by the operator.
Important: RTP is calculated over an enormous number of spins — millions or billions. In any single session, your actual results can be wildly different from the RTP. You might win 500% of your stake or lose everything. The RTP only guarantees the operator's long-term profitability, not your short-term experience.
For a deeper dive into RTP — including volatility, how to find a slot's RTP, and why your experience rarely matches the advertised number — see our RTP explained guide.
House edge by casino game
This table shows the house edge for every major game. It's the reference that tells you where your money goes furthest — and where the odds are worst.
| Game | House Edge | RTP | Notes |
|---|---|---|---|
| Video poker (Jacks or Better, optimal play) | 0.46% | 99.54% | Requires perfect strategy |
| Blackjack (basic strategy) | 0.5% | 99.5% | Varies by table rules; without strategy ~2% |
| Baccarat (banker bet) | 1.06% | 98.94% | Best standard baccarat bet |
| Baccarat (player bet) | 1.24% | 98.76% | Slightly worse than banker |
| French roulette (La Partage) | 1.35% | 98.65% | Half stake returned on even-money bets when 0 hits |
| Craps (pass / don't pass) | 1.41% | 98.59% | Among the best bets in the casino |
| European roulette | 2.70% | 97.30% | Single zero wheel |
| Online slots (high RTP) | 1–2% | 98–99% | e.g. Blood Suckers (98%), Mega Joker (99%) |
| Online slots (average) | 3–5% | 95–97% | Most mainstream slots |
| Blackjack (average player) | 2.0% | 98.0% | Most players don't use perfect strategy |
| American roulette | 5.26% | 94.74% | Double zero — significantly worse than European |
| Online slots (low RTP) | 8–15% | 85–92% | Some branded or progressive jackpot slots |
| Craps (proposition bets) | 11–17% | 83–89% | The worst bets on the craps table |
| Baccarat (tie bet) | 14.36% | 85.64% | One of the worst bets in any casino |
| Keno | 25–40% | 60–75% | Among the worst odds of any game |
| National Lottery (UK) | ~50% | ~50% | Half of ticket sales go to prizes |
| Sports betting (typical market) | 5–10% | 90–95% | Varies by bookmaker and market |
| Betting exchange | 2–5% | 95–98% | Commission-based, usually lower margin |
The pattern is clear: skill-based games with optimal strategy (video poker, blackjack) have the lowest house edges. Pure chance games with flashy production (branded slots, keno, lottery) have the highest. Our house edge calculator lets you see exactly what any house edge costs over any number of bets.
How much does the house edge actually cost you?
The house edge is abstract until you translate it into real money. Here's what different house edges cost over 100 bets at £10 per bet (£1,000 total wagered):
| House Edge | Expected Loss (100 bets × £10) | What That Means |
|---|---|---|
| 0.5% (blackjack, basic strategy) | £5.00 | Lose roughly 50p per hour at a typical pace |
| 1.06% (baccarat banker) | £10.60 | About £1 per hour |
| 2.70% (European roulette) | £27.00 | Nearly £3 every 10 minutes at a fast table |
| 5.26% (American roulette) | £52.60 | Double the cost of European roulette |
| 4% (average online slot) | £40.00 | At 600 spins/hour, this adds up fast |
| 10% (low RTP slot) | £100.00 | Lose 10% of everything you wager |
| 50% (National Lottery) | £500.00 | Half your money goes to the operator before prizes |
The hourly cost depends on how fast the game plays. Roulette might be 30–40 spins per hour in a land-based casino. Online slots can be 400–800 spins per hour. The faster the game, the faster the house edge erodes your bankroll — even if the percentage is moderate.
Why the house edge matters more than you think
It compounds with time
The house edge is per bet, not per session. The longer you play, the more bets you place, and the more your results converge toward the mathematical expectation. A 30-minute session might end anywhere. A 6-hour session at a game with a 4% house edge will almost certainly cost you money.
This is why casinos are designed to keep you playing: no clocks, no windows, free drinks, loyalty rewards. Every extra minute you stay increases the number of bets — and the number of bets is what turns the house edge from a theoretical percentage into a real cost.
It applies to your total wagered, not your initial deposit
If you deposit £100 and play roulette, you don't lose 2.70% of £100. You lose 2.70% of every bet you place. If you bet £10 per spin for 50 spins, you've wagered £500 — and your expected loss is £13.50, not £2.70. Recycling winnings means you wager far more than your initial deposit. This is how people lose more than they expected even at games with "low" house edges.
It can't be beaten by a system
No betting system — Martingale, Fibonacci, Labouchère, or anything else — can overcome the house edge in games of pure chance. These systems change the distribution of your wins and losses (more frequent small wins, less frequent large losses), but they don't change the expected value. Over time, the house edge applies regardless of your staking pattern.
The only games where skill can reduce the house edge are blackjack (basic strategy and card counting) and poker (where you play against other players, not the house). For every other game, the house edge is fixed by the rules and cannot be changed by your behaviour.
If you find that understanding the house edge is changing how you feel about your gambling — or if the numbers in this guide concern you — our self-assessment quiz is a confidential 2-minute check-in that can help you understand where you stand.
House edge in sports betting
Sports betting works differently from casino games. There's no fixed house edge per bet. Instead, the bookmaker builds a margin into the odds — called the overround (or vig).
If a football match has three possible outcomes (home win, draw, away win), fair odds would give implied probabilities totalling exactly 100%. But a bookmaker might price the market at 104% — the extra 4% is the margin.
The size of the overround varies:
- Major football leagues: 3–5% on popular markets
- Niche sports / lower leagues: 6–10%
- Betting exchanges: 2–3% (commission-based, lower margins)
The key difference from casino games: in sports betting, the outcome isn't purely random. Knowledge, research, and analysis can influence your results. This doesn't guarantee a profit — but it means the effective house edge for an informed bettor can be lower than the headline margin. For more on how bookmaker margins work, see our betting odds explained guide.
How to minimise the house edge
You can't eliminate the house edge, but you can choose where to spend your money:
- Choose games with the lowest edge. Blackjack with basic strategy (0.5%), baccarat banker (1.06%), and European roulette (2.70%) give you the most play for your money. Avoid American roulette, keno, and low-RTP slots.
- Learn optimal strategy. In blackjack, basic strategy reduces the house edge from ~2% to ~0.5%. In video poker, optimal play can push it below 0.5%. These aren't complex — basic strategy charts for both games are widely available and free.
- Play slower. Fewer bets per hour means less money exposed to the house edge. Land-based games are naturally slower than online. If you play online, take deliberate pauses between spins.
- Check RTP before playing slots. Reputable online casinos publish the RTP for each slot. Choose games above 96% and avoid branded or progressive jackpot slots (which often have RTPs of 85–92%).
- Use betting exchanges for sports. Exchange margins are typically 2–3% versus 5–10% at traditional bookmakers. The odds are set by other bettors, not the house.
The house edge is the most important number in gambling — and it's the one most players never check. Now you know what it is, how it varies by game, and what it actually costs. The choice of where and how long to play is yours, but at least now it's an informed one.
Frequently asked questions
Written by
David Burke
David is a gambling industry analyst and poker player based between London, Spain, and Malta. He has spent over a decade observing the European betting and casino landscape, with particular expertise in odds, probability, game strategy, and how the bookmaking industry works. At WiseStaker, David writes guides on bet types, game rules, and the mathematics behind gambling.
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