Many players try a game in demo mode first. That is a smart way to learn the rules, the features and the pace of a game without spending anything. But there is one thing demo play never shows you: what the game costs you over time. That cost is set by a single number, the house edge. Once you understand it, you can compare a roulette wheel and a slot machine on equal terms.
What the house edge is
The house edge is the share of every bet that the casino expects to keep in the long run. It is not a fee that is taken from each spin, and it does not tell you what will happen in your next session. It is an average over thousands of rounds. The higher the edge, the faster your bankroll shrinks on average.
Slots usually show the same idea from the other side, as RTP (return to player). A slot with an RTP of 96% has a house edge of 4%. Roulette rarely lists an RTP, because the edge follows directly from the wheel itself.
Why roulette is easy to calculate
Roulette pays as if the zero did not exist. A straight-up bet on one number pays 35 to 1, which would be a fair price on a wheel with 36 numbers. The zero pockets are where the casino earns its money. That gives these edges:
- European roulette (one zero, 37 pockets): 1/37 = 2.70%.
- French roulette with La Partage on even-money bets: 1.35% on those bets, because half the stake is returned when the ball lands on zero.
- American roulette (zero and double zero, 38 pockets): 2/38 = 5.26%.
- Triple-zero roulette (39 pockets): 3/39 = 7.69%.
Because the maths is this clean, every bet on the same wheel has the same edge, with the exception of La Partage and a few special bets. For a full breakdown per variant and per bet type, see this explanation of the house edge in roulette.
Slots: same idea, less transparency
A slot's house edge comes from its RTP, and that is set by the game provider. Many popular slots sit somewhere between 94% and 97% RTP, which means an edge of roughly 3% to 6%. Two things make slots harder to judge than roulette:
- Some providers release the same game with several RTP settings, and the casino chooses which one it offers. The version in a demo is not always the version in the real-money lobby.
- Volatility hides the edge. A high-volatility slot can pay nothing for a long time and then one large win. That feels very different from roulette, but the long-run cost is still the edge.
Speed matters as much as the percentage
The edge applies to every euro or dollar you wager, not to your deposit. That makes the number of rounds per hour just as important as the percentage itself. A simple example on European roulette: 100 spins of 10 per spin means 1,000 wagered. At 2.70%, the expected loss is 27.
Slots are usually much faster than a roulette table, especially with autoplay or turbo modes. A slot with a slightly higher RTP can therefore still cost more per hour than a roulette wheel, simply because you play many more rounds.
Betting systems do not change the maths
Systems such as the Martingale (doubling your stake after every loss) change how your results are spread out: many small wins and occasionally a very large loss. They do not change the expected result. Every spin still carries the same edge, so the total expected loss is always the edge multiplied by the total amount you wager.
How to use this when you play
- Choose single-zero roulette over double or triple zero whenever you have the choice.
- Check the RTP in a slot's info screen in the real-money version, not only in the demo.
- Think in total amount wagered, not in deposits, and set a budget for that.
- Use demo mode to learn a game, not to "test" a strategy. A demo session that went well says nothing about the edge.
The house edge is not a reason to never play. It is the price of the entertainment. Knowing that price makes it much easier to decide which game is worth your time and your budget.
