The rule in one line
Bet on an even-money outcome like red or black, double the stake after each loss, and go back to the base bet after a win. Lose 1, 2, then win 4, and you recover the 3 you lost plus 1. The longer the losing run, the faster the required stake grows: 1, 2, 4, 8, 16, 32, 64, 128 times the base bet.
How many losses end it
With a base bet of 1 unit, losses pile up as 1+2+4+…, and once you cannot cover the next stake you have to bet whatever is left. On a European wheel the chance of losing a single red bet is 19/37 (about 51.4%).
| Bankroll | Losses in a row you survive | Streak that busts you | Chance of that streak starting now | Chance it happens at least once in 300 spins |
|---|---|---|---|---|
| 100 units | 6 (63 units lost) | 7 | about 0.94% | about 75% |
| 500 units | 8 (255 units lost) | 9 | about 0.25% | about 30% |
| 1,000 units | 9 (511 units lost) | 10 | about 0.13% | about 17% (about 46% over 1,000 spins) |
This uses the starting balance. Winnings along the way can buy you one more step. Still, a bankroll ten times larger only lets you survive about three more losses, because your money grows linearly while the stake doubles.
Three walls that cause ruin
- The bankroll wall: after a handful of losses you cannot place the next bet. A win always earns one base unit; a loss costs dozens or hundreds.
- The table-limit wall: every table has a maximum bet, so after a certain streak you cannot double again. Once you hit it, a win no longer recovers your losses.
- The house-edge wall: the green zero makes your win chance lower than 50%. Whatever order you bet in, about 2.7% of everything you wager on a European wheel goes to the house. The arithmetic is in European vs American house edge.
Break it yourself in the app
the Android app Martingale Bust runs the same rule for hundreds or thousands of spins with no real money and plots the result as a balance curve.
The app shows amounts in Korean won (₩) in every language. Treat them as abstract units; only the ratios matter.
Choose a bankroll and base bet
On the Simulator tab, pick a starting bankroll, a base bet, the roulette type (European or American), the table bet limit, a cash-out goal and the speed, then tap Start Simulation.
Watch the curve collapse
The balance climbs in small steps, then drops straight down on one long losing run. Below the curve you can read spins played, peak balance, wins and losses, actual win rate and the longest losing streak. Going bust with a win rate above 50% is common.
Turn on a table limit and run again
Set the table bet limit to 64 times the base bet and the stake stops growing at the seventh bet. You can see on the curve that a win after hitting the limit leaves you still in the red.
FAQ
Wouldn’t it work with unlimited money?
Only in a world with unlimited money and no table limit. Real bankrolls, limits and time are finite, and under those conditions the expected value is always negative.
What if the base bet is tiny?
You survive a few more losses, but each win also earns less, and 2.7% of everything you wager still leaks away.
Can I bet real money in the app?
No. All amounts are virtual and there is no payment or cash-out feature.
Sources: Wikipedia, Gambler’s fallacy (Monte Carlo 1913)
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.