House edge: why casinos always win (except when they don't)
Every casino game carries a number the casino would rather you feel than read. It's called the house edge: the percentage of each bet the house expects to keep over the long run. Double-zero roulette carries an edge of 5.26%, which means that across enough spins, every $100 pushed through that wheel sends about $5.26 to the casino. Not per losing night. Per hundred dollars wagered, forever.
This is not a scam and it isn't bad luck. It's arithmetic, built into the payouts before you ever sit down, and it's why the industry can pay for the fountains. But the edge is not the same size everywhere, and in a small handful of games it can be shrunk, erased, or — in exactly one famous case — flipped. Knowing which games are which is the single most useful piece of gambling math there is.
What the edge actually is
Take the roulette example apart and the whole concept falls out. An American wheel has 38 pockets: numbers 1 through 36, a zero, and a double zero. Bet a single number and a win pays 35-to-1, but with 38 pockets, fair odds would be 37-to-1. That two-unit shortfall works out to 5.26%. The casino doesn't need to cheat; it just pays slightly less than the true odds, every time.
The edge says nothing about tonight. In the short run, variance dominates: people walk away winners every single day, and the casino is genuinely happy to pay them, because the math doesn't need any particular player to lose. It needs millions of bets, and over millions of bets the percentage grinds through as reliably as gravity. That's the whole business model: sell variance to players, keep the expectation.
The numbers, game by game
House edge varies enormously from one game to the next — far more than most players realize. These figures come from the Wizard of Odds house-edge table and, for slots, from UNLV's Center for Gaming Research; where skill is involved, they assume you play correctly.
The gap between the best and worst common games is more than a factor of ten. And the two cheapest table games could not be more different: baccarat asks nothing of you, while blackjack's number is a reward you only collect by playing every hand right.
- Double-zero roulette: 5.26% on nearly every bet — the layout offers variety, not better odds.
- Slot machines: commonly 5-10%. Nevada's statewide average hold was about 7.1% in 2025, and roughly 7.5% on the Strip.
- Craps, pass line: 1.41% — one of the best simple bets in the building.
- Baccarat: 1.06% on the banker bet, 1.24% on player. No decisions, no skill, surprisingly cheap.
- Blackjack with perfect basic strategy: roughly 0.5% under decent rules, as low as 0.28% under the most liberal Vegas Strip rules. Play by feel instead and you hand a chunk of that back.
Why you can't outplay a roulette wheel
Roulette, craps, slots and baccarat share one property that makes their edges permanent: every trial is independent. The wheel has no memory. A number that hasn't hit in fifty spins is exactly as likely as any other on spin fifty-one. Nothing you observe, record, or feel changes the probability of the next outcome, so there is no information for skill to act on. Every spin is the same spin.
Betting systems don't touch this. Martingale, Fibonacci, streak-chasing — all of them just rearrange which nights you lose. Every bet in the sequence still carries the same negative expectation, and no combination of negative-expectation bets adds up to a positive one. The scoreboard at the baccarat table showing the last thirty outcomes is decoration. The casino installed it, which should tell you what it's worth.
The exception: games with memory
Blackjack is different for one structural reason: it's dealt from a depleting deck. Every card that hits the felt changes the composition of what remains, which means — unlike the wheel — the game remembers. And the remaining cards matter: a shoe rich in tens and aces favors the player, because blackjacks (paid 3-to-2) come more often and the dealer, who must hit stiff hands, busts more often. A shoe rich in small cards favors the house.
Card counting is nothing more than tracking that drift and betting more when the remainder favors you. Done well, it doesn't just shrink the half-percent edge — it flips it: the Wizard of Odds puts a realistic counter's advantage at 0.5% to 1.5%. Honesty requires the caveats. That's a thin edge carried on brutal variance, it takes real bankroll and flawless play to survive, and casinos push back with shuffles and back-offs. Nobody should count cards expecting to get rich. But the math genuinely inverts, which no roulette system has ever truthfully claimed.
The other exception: no house at all
Poker, hearts, spades, euchre, bridge, gin rummy — these games have no house edge because there is no house in the game. You play against other people, and (poker's rake aside) every chip or point you win comes from an opponent, not from odds engineered against the table. There is no structural percentage to overcome. There are only better and worse players.
The skill in these games is hidden information: remembering what's been played, working out who's void in a suit, reading a discard, inferring a holding from a bid. It's the same muscle as counting a shoe — building a picture of unseen cards from the ones you've watched go by — except here the edge it buys you isn't capped at a percent and a half. It's as large as the gap between you and the person across the table.
What to do with all of this
You can't outplay a roulette wheel, and you shouldn't try. If you enjoy pure-chance games, play them as entertainment with a known price tag, because no system, streak, or lucky table changes the number.
But you can out-study a deck, and you can out-study an opponent. Blackjack rewards memorized strategy and a disciplined count. The player-versus-player games reward inference and attention, with no house percentage skimming the pot at all. Study pays exactly where the game has memory or a human across the table — so that's where the studying should go.
Skill only pays in games that remember — a depleting shoe, a folded discard, an opponent's habits. Those are the games you can actually train for, and every trainer here is free.
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