Count the pockets
| Wheel | Pockets | Red | Chance a red bet wins | House edge (even money) |
|---|---|---|---|---|
| European (single zero) | 37 (1–36 + 0) | 18 | 18/37 ≈ 48.65% | 1/37 ≈ 2.70% |
| American (double zero) | 38 (1–36 + 0 + 00) | 18 | 18/38 ≈ 47.37% | 2/38 ≈ 5.26% |
An even-money bet pays what you staked when it wins and loses the stake otherwise. When 0 or 00 lands, both red and black lose. (Special rules some casinos use, such as returning half an even-money bet on zero, are not covered here.)
Expected value
Expected value = (chance of winning × amount won) − (chance of losing × amount lost).
| $10 on red | Calculation | Average per spin |
|---|---|---|
| European | 10 × 18/37 − 10 × 19/37 | about −$0.27 |
| American | 10 × 18/38 − 10 × 20/38 | about −$0.53 |
Twenty-seven cents looks trivial. It is not a cost you pay now and then; it is the average slice taken from every single bet.
When spins add up
| $10 a spin for 1,000 spins ($10,000 wagered) | Expected loss |
|---|---|
| European | about $270 |
| American | about $526 |
What drives the loss is total action, the sum of all stakes. The Martingale raises stakes during losing runs, so for the same number of spins it wagers more and expects to lose more.
Why no system changes it
If every bet has negative expected value, the sum of any sequence of those bets is negative too, however you size them. A betting system only changes the shape of the outcome: frequent small wins and rare big losses, or the reverse. That shape is the subject of why winning often still loses.
Switch wheels in the app
The app shows amounts in Korean won (₩) in every language. Treat them as abstract units; only the ratios matter.
Choose European or American
In Bet Setup, pick European or American under Roulette type; the win rate (48.6% or 47.4%) appears right below. Run both with the same bankroll and base bet and compare how many spins it takes to go bust.
Compare probabilities on the Stats tab
The Stats tab repeats the same setup hundreds or thousands of times and reports the bankruptcy rate and average spins survived. Switching to American shows ruin arriving sooner, in numbers.
FAQ
Is a single-number bet better because it pays more?
At the standard 35-to-1 payout, a straight-up bet on a European wheel has the same 1/37 edge. A bigger payout means bigger swings, not a better average.
With a 2.7% edge, will I lose only $27 if I bring $1,000?
No. The 2.7% applies to the total you wager, not the cash you bring. Recycling the same money through many bets can lose more than you started with on the table.
Martingale Bust - Roulette Sure-Win Simulator
Every amount is virtual. No sign-up, works offline. A free Android app for learning probability, in English and Korean.