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Explaining the En Prison and La Partage rules in roulette


27 Sep 2017

It could easily be overlooked sometimes that 37 numbers exist on a European roulette wheel.

The reason for this forgetfulness relates to the fact that casinos pay out all winning bets as if there are 36 numbers on a wheel. It’s as good as forgotten that the green zero is a feature on the wheel.

For example, if a person bets straight up on a number, probability suggests that they have a one in 37 chance of being a winner. However, should their bet be fruitful, they are only paid 36/1.

Therefore, the green zero symbolises the house edge. Players are effectively being paid out 2.7% less than they should be for accepting a 36/1 payout for a winning bet that has a 37/1 chance of being successful.

For those playing on American roulette tables containing both a green 0 and a green 00, the house edge is tilted even further in favour of the casino at 5.4%. This is because a player would get paid out at 36/1 for a bet that has a one in 38 probability of winning.

The inclusion of the 00 on the American wheel isn’t the only difference with its European equivalent. Here are some other differences between the pair.

Even money bets

The house edge is not just a factor on straight-up bets. It also exists on the so-called even money bets.

These are those perceived to have a 50/50 chance of winning, such as red against black or odd numbers against even.

Players are paid at 1/1 if correctly betting on any of these markets, meaning if they stake £20, they get their bet back, plus another £20 on top.

However, again because of the green zero, their chances of success on such markets are not 18/36, but 18/37. As a result, a player should be paid out 102.7% of their original bet and not 100%.

For those betting £20, they are theoretically being short-changed 54p on every winning bet because of the house edge.

But some casinos do offer incentives as a way of reducing this house edge.

Below are two specific rules which originated in France, but have found their ways to other casinos around the world.

La Partage

It should be remembered that the 0 shouldn’t always be considered a negative. After all, players can bet directly on it like they can any other number and it’s just as likely to be a winner.

And with the La Partage rule, if it is the winning number, losing even money bets are not complete losers.

Instead, half of the losing stake is returned to the player, softening the blow somewhat. What this also does is commendably reduce the house edge to 1.35%.

Should a person bet on their black lucky number 11 and red 34 is the winning number, they do not get such a perk and lose their whole stake.

En Prison

If a person is put in prison, they are secure, padlocked up and restrained. So is someone’s even money bet if the ball is spun and lands on zero and a casino is offering the En Prison roulette rule.

Instead of being given half of their losing stake back like the La Partage rule does, with En Prison it effectively rolls over to the following spin.

Should the original bet be successful on this next spin, the player will receive their full stake back, but, crucially, not the winnings they would have initially been due.

So if a person had bet £20 on black, this would be imprisoned after the first spin of zero, but if on the second spin the ball finished in black 31, a player would get their £20 returned. However, they obviously would have received £40 had the 31 landed on the original spin.

Like La Partage, the En Prison rule also reduces the house edge from 2.7% to 1.35%.

Free chips

As a way of enticing in more visitors, it isn’t uncommon for a casino to place free-chip vouchers in nearby hotel rooms. A person would then cash these vouchers in at the casino as bonus chips, which have to be wagered before being able to be cashed out.

Should a player have two such £5 vouchers, it isn’t an uncommon strategy to cash them in and stake one on red and one on black.

Whichever wins would net this player £10 in real chips which would then be allowed to be cashed out. The only way this plan fails is if the green zero is the winning number in this specific hand, rendering both the red and black bets losers.

If this strategy was carried out at a casino offering either the La Partage or En Prison rules, the chances of leaving with real profit would be enhanced.