House Edge

The house edge is the reason casinos exist. It is built into the rules of every game, it does not depend on luck, and no betting pattern removes it. Understanding exactly what it is, and what it is not, is probably the single most useful thing on this site.

Where it comes from

The house edge is the gap between the true odds of an outcome and the odds the casino pays for it.

European roulette is the cleanest illustration. The wheel has 37 pockets: numbers 1 to 36 plus a single zero. Bet on a single number and your chance of winning is 1 in 37. Fair odds would pay 36 to 1. The casino pays 35 to 1.

That missing unit is the entire business. Over 37 spins of £1 each, you expect to win once, receiving £36. You staked £37. The £1 difference is 1/37 of turnover, or 2.70%.

Nothing about that calculation involves luck. It is a property of the payout table.

House edge and RTP are the same fact

Return to player is the house edge stated from the player’s side, and the two always sum to 100%:

Game	House edge	RTP
Blackjack (basic strategy)	0.5%	99.5%
Baccarat (banker bet)	1.06%	98.94%
Craps (pass line)	1.41%	98.59%
European roulette	2.70%	97.30%
American roulette	5.26%	94.74%
Online slots	2–10%	90–98%
Keno	20–30%	70–80%

The spread is enormous. Keno takes forty times more per pound staked than blackjack does.

Per bet, not per session

The edge applies to turnover, every pound that passes through the game, not to your deposit.

Take £100 to a 2.7% roulette table. Stake it all once and you expect to lose £2.70. But you do not stake it once; you stake it, collect what comes back, and stake again. Thirty spins of £10 is £300 of turnover, and the expected loss is £8.10, not £2.70.

This is why playing time is the real variable. The edge is charged per bet, so the longer you play, the more certainly the theoretical figure becomes the actual one. A short session can beat any edge. A long one essentially cannot.

What it does not tell you

The house edge is an average across an enormous sample, and it says nothing about a session. Two games with identical edges can feel completely different depending on volatility, one grinding slowly downward, the other paying nothing for an hour and then everything at once.

It also assumes correct play where play matters. Blackjack’s 0.5% requires basic strategy on every hand; deviate on instinct and the real edge against you is closer to 2%. Roulette’s 2.7% is fixed regardless, because no decision you make changes the wheel.

Finally, the edge is not a schedule. Losing £2.70 per £100 does not mean losing steadily. It means that across millions of bets the average converges there, while any particular hundred bets does more or less whatever it likes.

The one decision that actually matters

Given all that, the practical takeaway is narrow but genuinely useful: choose lower-edge games, and be aware of how much turnover you are generating.

Avoid American roulette wherever European is available. Same game, nearly double the cost. Treat side bets with suspicion; they almost always carry several times the edge of the main game. And note that the games with the lowest edges are the ones that game weighting excludes from bonus clearing, which is not a coincidence.