D'Alembert Roulette System: The Gentle One-Unit Progression
Add one unit after a loss, subtract one after a win. The lowest-volatility progression on this site - and a textbook example of a gambler's fallacy dressed up as a system.
- Type: negative progression
- Risk: moderate
- Best bet: even-money
D'Alembert raises the stake by one unit after each loss and lowers it by one after each win. The premise is that, over a session, wins and losses roughly balance, leaving you ahead by about one unit per win. The progression is gentle and easy to follow, but the premise is flawed: spins are independent and the zero gives the house its edge, so a run with more losses than wins erodes the bankroll and the long-term expected value stays negative.
Quick facts
| System type | Negative progression (linear, ±1 unit) |
|---|---|
| Best known use | Low-volatility even-money sessions |
| Typical bet type | Red/black, odd/even, high/low |
| Progression style | Add one unit on loss, drop one on win |
| Risk level | Moderate |
| Bankroll pressure | Moderate - slow to build |
| Table-limit pressure | Low - linear growth |
| Main weakness | Assumes balance that the zero prevents |
How the system works
Start at a base unit. After every loss, increase the next bet by one unit; after every win, decrease it by one unit (never below the base). When you have had as many wins as losses, you are ahead by roughly the number of wins in units. The linear step keeps stakes far below what doubling would demand.
Step-by-step example
Unit = $5:
| Spin | Bet | Result | Net |
|---|---|---|---|
| 1 | $5 | Loss | −$5 |
| 2 | $10 | Loss | −$15 |
| 3 | $15 | Win | $0 |
| 4 | $10 | Win | +$10 |
| 5 | $5 | Win | +$15 |
Equal wins and losses left a small profit. But reverse the order - three losses first - and the bankroll dips deeper before any recovery.
Best bet types for the system
Even-money bets are the natural fit, since the system leans on the assumption of a roughly 50/50 outcome. On longer-paying bets the "one unit per win" logic falls apart.
What happens during a losing streak
Each loss adds just one unit, so after eight losses you are betting nine units, not 256. The drawdown is shallow and slow - which is genuinely safer, but also lulls players into staying at the table far longer, giving the house edge more spins to work.
Bankroll and table-limit risk
Both are modest. The linear growth rarely threatens a table maximum, and bankroll erosion is gradual. The real cost is time-on-table: the longer you play, the more certainly the edge asserts itself. The survival calculator shows how a D'Alembert line grows compared with steeper systems.
European vs American roulette impact
Because D'Alembert relies on near-balance, the extra double-zero pocket on American wheels hurts it directly - it tilts the win/loss balance further against you. Stick to European or French La Partage.
Strengths and weaknesses
Strengths
- Very low volatility
- Simple ±1 rule
- Shallow drawdowns
- Rarely hits table limits
Weaknesses
- Built on a gambler's fallacy
- Long play feeds the edge
- Loss-heavy runs still erode funds
- Negative expected value
Who the system may suit
Players who prioritise long, low-stress sessions with small swings, and who understand that "gentle" does not mean "winning". Good for getting a feel for a game without big variance.
Who should avoid it
Anyone who believes the win/loss balance is guaranteed, and anyone chasing meaningful profit - the per-win edge is tiny and still negative overall.
Testing advice
Set a spin cap, not just a money cap, because D'Alembert's danger is time. Compare its smooth curve against Martingale and Fibonacci in the showdown, and confirm the even-money EV with the odds calculator.
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Frequently Asked Questions
Raise the bet one unit after a loss, lower it one unit after a win. Equal wins and losses leave a small profit in units.
Lower volatility than doubling systems, yes. But loss-heavy runs still erode funds and the EV stays negative.
Even-money bets, which support the assumption that wins and losses roughly balance.
No. The balance assumption ignores the zero, which is exactly where the edge lives.
Its gentle, trackable progression suits beginners who want low volatility and understand it is not profitable.