D’Alembert Betting System

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Updated on: August 3rd, 2021

The D’Alembert system of gambling is one of the most irregular betting systems. There is no particular structure to it and is often referred to as the “Gambler’s Fallacy”. Fallacy because it is based on gut feeling not calculation. All other betting systems are based on mathematical probability. The D’Alembert gambling strategy assumes the next outcome based on how rarely it has appeared in previous instances. Confused? Let’s get into how this gambling system works.

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The D’Alembert Gambling Principle

Much like the Martingale strategy, the D’Alembert gambling strategy is based on a coin toss. Therefore, it should be used on even money wagers or bets on one of two outcomes. The D’Alembert strategy is used mostly in roulette.

In theory, the D’Alembert betting system assumes that an outcome has higher probability of occurring if it has occurred less than usual in the past. This is not true however because if heads has a 50% chance in a coin toss chances will still remain at 50% regardless of how frequent a tails outcome is.

D’Alembert Betting System

How does D’Alembert Work?

The D’Alembert system works based on the assumption that probability is inversely proportion to previous outcomes. So

  • Establish a base unit
  • Your first bet is equal to the base stake
  • After a loss increase the stake by one base unit
  • The next wager after you win must be decreased by one base unit. Unless you won on the first bet then keep the stake the same.

While we do not recommend this betting system, if you are going to use it there are some useful tips.

Do not make your base unit of your stake more than 5% of your entire bankroll. If you want longevity, keep your base unite of wagering between 1% – 2% of your total bankroll.

The D’Alembert Gambling System in Practice

Here’s How the d’Alembert Strategy works in practice

If you have established your base unit as $10 this how it would work

Wager Amount Outcome Play
$10 Lose Increase stake by a $10 -$10
$20 Lose Increase stake by a $10 -$20
$30 Win Decrease stake by a $10 +$60
$20 Lose Increase stake by a $10 -$20
$30 Lose Increase stake by a $10 -$30
$40 Win Bankroll Depleted +$80


  • Total wagered = $150
  • Total won $60


In even money bets, the probability of an outcome is independent of the previous. In fact, this is true for any wagers. Each outcome is a unique event. Therefore, if it’s a coin-toss bet that is, a bet between two outcomes like red or black on roulette, the probability is constant. If the previous outcomes have been blacks, it does not automatically follow that the opposite outcome. In a coin toss, the first bet has odds of 50% for each outcome. And because each new coin toss is just like the first coin toss the probability of either heads or tails is still 50%.

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