How it works
You bet on an even-money outcome and choose a unit, say €5. After a loss, you add one unit to your next bet. After a win, you remove one unit, never going below one unit.
The idea behind it
The system assumes that wins and losses will even out, so after a loss, a win becomes more likely. That's the gambler's fallacy: at roulette, each spin is independent, and red is never 'due'.
What a losing streak costs
Bets grow slowly, which is why the D'Alembert feels safe. Starting at one unit, ten losses in a row mean bets of 1 to 10 units, 55 units lost in total (€275 with a €5 unit), and the next bet is 11 units.
Why it doesn't beat the casino
Even-money bets win slightly less than half the time (18 out of 37 on European roulette), so over time losses outnumber wins and your bets drift upwards. The house edge, 2.7% on European roulette, applies to every euro you bet.
Our verdict
Myth. The D'Alembert has small swings, but it doesn't change the house edge. It's a way to size bets, not a way to win.
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FAQ
Does the D'Alembert work?
No. It relies on the gambler's fallacy and doesn't change the house edge.
Is the D'Alembert safer than the Martingale?
Its bets rise much more slowly, so losses build up gradually rather than all at once, but the house edge is the same.
Related guides
Strategy and maths reduce the house edge, but never remove it. 18+, play responsibly.