What Is the House Edge?
The house edge is the mathematical advantage that 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. It doesn't mean you'll lose that exact percentage in one session — but over millions of bets across all players, that percentage consistently flows to the house.
For example, a house edge of 5% means that for every $100 wagered over time, the casino retains $5 on average. The remaining $95 cycles back to players as winnings.
Why the House Always Has an Edge
Casinos build a slight mathematical advantage into the rules of every game. The edge comes from different mechanisms depending on the game:
- Slots — Payout schedules are set so that payouts total less than the probability-weighted value.
- Roulette — The zero (and double zero in American roulette) creates a mismatch between true odds and payout odds.
- Blackjack — Players act before the dealer, so player busts lose even if the dealer would also have busted.
- Baccarat — The 5% commission on Banker wins accounts for the edge.
House Edge by Game
| Game | Approximate House Edge | Notes |
|---|---|---|
| Blackjack (Basic Strategy) | 0.5% or less | With perfect basic strategy |
| Baccarat (Banker Bet) | ~1.06% | Best bet in baccarat |
| Craps (Pass Line) | ~1.41% | One of the better craps bets |
| European Roulette | ~2.7% | Single zero wheel |
| American Roulette | ~5.26% | Double zero adds extra edge |
| Slot Machines | 2% – 15% | Highly variable by title |
| Keno | 20% – 35% | Among the worst odds |
The Difference Between Odds and Payouts
Understanding the gap between true odds and payout odds reveals exactly where the house edge lives.
In European roulette, there are 37 numbers (1–36 plus zero). The true odds of hitting any single number are 1 in 37, or 36-to-1 against. But the casino pays only 35-to-1 on a winning single-number bet. That one unit difference across all winning bets is where the 2.7% house edge comes from.
How to Use This Knowledge
You can't eliminate the house edge, but you can choose games and bets that minimize it:
- Choose games with low house edges — Blackjack with basic strategy, baccarat banker bets, and craps pass line bets are among the best.
- Avoid high-edge bets — Roulette's five-number bet (in American roulette), keno, and many slot side bets carry disproportionate house edges.
- Learn optimal strategy — In skill-based games like blackjack or video poker, playing correctly makes a measurable difference to the house edge.
- Understand it's long-run math — Short sessions are driven by variance. The house edge becomes increasingly dominant over thousands of bets.
The Takeaway
The house edge is not a conspiracy — it's simply how casinos operate as businesses. Understanding it empowers you to make smarter choices: pick better games, make better bets, and set realistic expectations. Knowledge of the house edge is the single most useful piece of information any casino player can have.