What Is the House Edge?
The house edge is the mathematical advantage a casino holds over players in any given game. It's expressed as a percentage of each bet that the casino expects to keep over the long run. For example, a 2% house edge means that for every $100 wagered, the casino expects to retain $2 on average.
The house edge doesn't mean you lose 2% of your money every session — in the short term, anything can happen. But over thousands of bets across thousands of players, the edge ensures the casino is always profitable.
How Is It Calculated?
The house edge comes from a mismatch between the true odds of an event and the payout odds the casino offers. A classic example is roulette:
- An American roulette wheel has 38 pockets (numbers 1–36, plus 0 and 00).
- The true odds of hitting a single number are 37 to 1.
- The casino pays out 35 to 1 — keeping 2 units of profit per win.
- This gives American roulette a house edge of 5.26%.
European roulette, with only a single 0, has a house edge of about 2.7% — considerably better for the player.
House Edge by Game: A Comparison
| Game | Approximate House Edge | Notes |
|---|---|---|
| Blackjack (basic strategy) | 0.5% or less | Depends on rules; best with fewer decks |
| Baccarat (banker bet) | ~1.06% | One of the lowest in the casino |
| Craps (pass line) | ~1.41% | Fair game with simple bets |
| European Roulette | ~2.7% | Single zero only |
| American Roulette | ~5.26% | Avoid if European is available |
| Slots | 2%–15%+ | Varies widely; rarely disclosed |
| Keno | 20%–35% | Among the worst for players |
Expected Value: The Player's Perspective
Expected value (EV) is the flip side of the house edge — it tells you what you can expect to gain or lose per bet on average. For casino games, EV is almost always negative for the player (that's the point of the house edge).
Formula: EV = (Probability of Win × Amount Won) – (Probability of Loss × Amount Lost)
Understanding EV helps you make rational choices. A slot machine with a 10% house edge is a much worse value than a blackjack hand played correctly, even if both "feel" similar in the short term.
Variance vs. Edge: Why Short-Term Results Differ
The house edge is a long-run concept. In any single session, variance (the swings in outcome) can work in your favor dramatically. High-variance games like slots or roulette produce wild short-term swings — big wins and big losses. Low-variance games like blackjack tend to produce more consistent, gradual outcomes.
This is why people win at casino games sometimes — variance is real. But it doesn't contradict the house edge; it's a feature of how probability works over small sample sizes.
How to Use This Knowledge Practically
- Choose lower-edge games — Blackjack, baccarat, and craps give you the best mathematical footing.
- Learn correct strategy — Games like blackjack reward skill; wrong decisions raise your effective house edge.
- Set a budget — The house edge guarantees that longer play costs more. A session budget limits exposure.
- Avoid sucker bets — Insurance in blackjack, tie bets in baccarat, and proposition bets in craps often carry edges of 5–15%.
The house edge isn't something you can overcome with strategy or luck consistently. But understanding it transforms you from a passive player into an informed one — and that always makes for a smarter, more enjoyable experience.