The basic rule
How does the Martingale system work in roulette? The idea is to bet on an even-money outcome, such as red or black, and double the stake after each loss. When a bet finally wins, the player stops the sequence and usually returns to the starting stake on the next spin.
Suppose the initial stake is one unit: after a loss, the next bet is two units; if that also loses, the following bet is four. If the four-unit bet wins, its net payout is four units, which covers the previous losses of one and two units and leaves one unit in net profit. That outcome depends on a win arriving before the player can no longer increase the stake.
What the progression can—and cannot—do
The progression can recover earlier losses after a win, provided the winning bet pays an amount equal to the stake and the player has enough money and the table allows the next bet. It does not change the odds of the next spin. Past results do not make red, black, odd, or even more likely on the next spin; a losing streak, by itself, does not mean a win is “due.”
The arithmetic also shows the cost of a streak: after each loss, the required stake doubles, and the total already lost rises quickly. A finite bankroll or maximum table bet can stop the progression before recovery. In that case, the player is left with the accumulated losses rather than the small gain they were aiming for. Roulette also includes green outcomes, which are not among the two options in an even-money bet, so those options should not be treated as perfectly balanced on an actual table.
A practical example and a caution
In practice, someone who starts with one unit and loses three times would need to bet two, four, and then eight units. If the eight-unit bet wins, its net profit covers the earlier losses of one, two, and four units and leaves one unit of gain. But if the next bet also loses, the following stake would have to be even larger. This example explains the mechanics; it does not guarantee an outcome. The longer the losing streak, the more capital the progression requires.
Bettbit publicly lists Roulette in its catalogue. Martingale is a way to size bets, not a method for predicting outcomes or eliminating the house edge. Setting a loss limit and avoiding attempts to win losses back by increasing stakes can help prevent a progression from turning a limited loss into growing exposure.