House edge

The edge comes from the gap between the true odds of a bet and the odds the game actually pays. Take every possible outcome, multiply what the player wins or loses on it by its probability, and add the results together; the negative figure left over, divided by the stake, is the house edge.

European roulette shows the mechanism cleanly. The wheel has 37 pockets, but a straight-up bet pays 35 to 1, as though there were only 36. Over 37 spins of €1 the player wins €35 once and loses €1 on the other 36, so €1 of every €37 staked stays with the table. That is the 2.70% figure, and it holds for nearly every bet on the layout because the payouts are all scaled the same way.

Add a second zero and the same arithmetic gives 5.26%.

Baccarat needs a different step, because the Banker hand wins more often than the Player hand. In an eight-deck game Banker wins about 45.86% of rounds and Player about 44.62%, with ties in roughly 9.52%. Paid at even money, Banker would favour the player, so a 5% commission on winning Banker bets is taken, which leaves an edge of 1.06% against 1.24% on Player.

The edge belongs to each bet rather than to a whole game, and the spread inside one table can be wide. The baccarat Tie bet pays 8 to 1 on an outcome that lands about 9.52% of the time, which works out at 14.36%, more than thirteen times the cost of a Banker bet at the same table. Where a table pays 9 to 1 on the Tie, the edge on that bet drops to about 4.84%.

Rule variations move the figure too. French roulette tables with la partage or en prison return half of an even-money stake when zero lands, which halves the edge on those bets to 1.35%. In blackjack the number of decks, whether the dealer stands on soft 17 and what a blackjack pays all shift the edge, and so do the player’s own decisions; there is no single blackjack figure that applies to every table.

Practice varies between operators, so the rules panel of the specific table is the only reliable place to read the payouts.

What it means in money

The edge is charged on the total amount wagered, not on the money brought to the table. A player who arrives with €100 and stakes €10 a spin on European roulette for 200 spins has put €2,000 through the game, and the expected cost of that is about €54. Any one evening can land far above or below that, which is exactly why one session proves nothing about a game.

RTP, or return to player, is the house edge seen from the other side: a bet with a 1.06% edge has an RTP of 98.94%, and the two always add up to 100%. Table games tend to be described by their edge and slots by their RTP, but the quantity is the same.

Slots add one complication that table games do not have. Studios often release the same title in several RTP versions, and the casino chooses which one to offer, so the figure in one game’s help screen at one site does not automatically carry over to the identical-looking game elsewhere. What I check first is the RTP stated inside the game itself on that site, rather than the figure from the studio’s marketing.

Volatility is the measure most often confused with the edge, and it describes something else entirely. Two bets can share a 2.70% edge while behaving very differently: an even-money roulette bet wins often and in small amounts, while a straight-up number wins rarely and big. The edge sets the average cost; volatility sets how wildly results swing around that average on the way there.

No betting system changes the edge.