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An Analysis of the Contra Bet (contra d’Alembert) System

As one of the most popular roulette betting systems, the d'Alembert strategy has many variants and some of them are more common than others. The Contra Bet system, also known as Reverse d'Alembert, is one of them and is used by most players. We can say that it has very simple mechanics and it is possible to see the basic rules of progressive betting strategies in it. But the important thing is whether it works: is Contra Bet a system that gives you an advantage? We will answer this question below and see how useful it is with simulator tests.

Main features of the Contra Bet system

Like all progressive betting strategies, the Contra Bet system starts with two things: determining the initial wager (baseline) and using bets that only pay 1:1. For the former, it is recommended to use 1% of your bankroll, for the latter, you only need to place red/black, odd/even, or low/high bets.

You can see these features in many other betting systems. The difference of the Contra Bet strategy is how the wager amount increases. Here, too, there are two simple rules:

  • If you win, you increase the wager amount up to the baseline.
  • If you lose, you reduce the wager amount by baseline.

For example, let's say you start playing with 10 AUD: if you win, you must place a 20 AUD wager on the next spin, and if you lose, you must return to the baseline value or reduce the wager amount by 10 AUD. Let's give an example for easier understanding.

Contra Bet Strategy


  • Spin 1

    You started playing with 10 AUD (baseline) and lost. You have to return to the baseline value and wager 10 AUD on the next spin.

  • Spin 2

    This time you won, so on the next spin, you must increase the wager amount by 10 AUD (10 + 10 = 20 AUD).

  • Spin 3

    Once again you have won, so the wager amount on the next spin should be 30 AUD (20 + 10).

  • Spin 4

    Let's say you win again: simply increase the wager amount by 10 AUD more (30 + 10 = 40 AUD).

  • Spin 5

    This time you lost: on the next spin, you must reduce the wager amount by 10 AUD (40 - 10 = 30 AUD).

Experimenting on the Contra Bet System with a simulator

So, does Contra Bet actually work? To find the answer to this question, we need to see what the long-term results are. For this purpose, we used a roulette simulator with random results and added three players to the simulation. Each of these players has a different bankroll, but they all do 500 spins. At the same time, each one begins with a different baseline.

Player # Bankroll Basic bet
1 500 5
2 1000 10
3 500 3

After all the spins were complete, we used Google Sheets to graph the results. Player 1's results were:

Contra Bet

This player went bankrupt on the 170th spin as his bankroll dropped to 5 AUD: he simply had no money left to continue. He got a positive result in the first 70 spins but was not so lucky in the next ones. After 100, his progression was almost always negative, except for statistical deviations. The second player was a little luckier:

Contra Bet strategy

This player was able to last longer because he has a larger bankroll. However, he ultimately went bankrupt as his baseline was also higher: by the time he got to the 469th spin, he had only 30 AUD left and could not continue any further.

Contra Bet System

Player 3, on the other hand, went bankrupt on the 242nd spin and could not continue: at this stage of the simulation, only 15 AUD remained in his bankroll. Despite having a lower baseline, we can say that the results are similar to Player 1.

Overall, none of the players made a profit: they all went bankrupt and the player with the highest bankroll lasted the longest. We were able to obtain positive results in our simulations for the classical d'Alembert system, but all results were negative for Contra Bet. This is reminiscent of the difference between the classic Martingale and the Reverse Martingale, but in this comparison, the latter was a negative progression system. Contra Bet, on the other hand, fails to deliver the expected results despite being a positive progression system.

Pros and cons of the Contra d'Alembert system

There's no real advantage to this system: if a positive progression system gives negative results, it doesn't work - it's that simple. However, it has all the disadvantages of positive progression systems. In other words, if the loss frequency is higher than expected, the risk of bankruptcy increases, and there is no possibility of recovering your losses in the short term.


This is one of the most disappointing d'Alembert variants. The most important advantage of positive progressive betting systems is that they definitely work in the long run. Because eventually you will win, and since you continued to increase the wager amount, the payout will be big enough to cover all your losses. The only problem is that you don't know when you will win, so these strategies require a big bankroll. In other words, positive progression systems always work if your bankroll is big enough until you start winning.

Contra Bet is also a positive progression system, but as the simulation results show, it is not that effective in the long run. It can completely consume a 1,000 AUD bankroll within 500 spins. Such a risk exists in other positive progression systems too, but Contra Bet is more affected by the win/loss cycle compared to them and takes longer to start working. You can still give it a shot if you have a minimum bankroll of 1,000 AUD, but there are many other positive progression systems with much better results: there is no real reason to choose Contra Bet over them.

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